A caliphate (Arabic: خِلافة khilāfah) is a state under the leadership of an Islamic steward known as a caliph (/ˈkælɪf, ˈkeɪ-/, Arabic: خَليفة khalīfah, ), a person considered a religious successor to the Islamic prophet Muhammad (Muhammad ibn ʿAbdullāh) and a leader of the entire Muslim community. Historically, the caliphates were polities based in Islam which developed into multi-ethnic trans-national empires.  During the medieval period, three major caliphates existed: the Rashidun Caliphate (632–661), the Umayyad Caliphate (661–750) and the Abbasid Caliphate (750–1258). The fourth major caliphate, the Ottoman Caliphate, established by the Ottoman Empire in 1517, was a manifestation whereby the Ottoman rulers claimed caliphal authority. During the history of Islam, a few other Muslim states, almost all of them hereditary monarchies, have claimed to be caliphates.
Prior to the rise of Muhammad and the unification of the Arab tribes of the Arabian Peninsula under Islam, the tribes of Arabia followed a pre-Islamic Arab polytheism, lived as self-governing sedentary and nomadic communities and often raided their neighbouring tribes.   Following the conquests under Muhammad of the Arabian Peninsula, the region became unified and most of the tribes adopted Islam. 
The first caliphate, the Rashidun Caliphate, was established immediately after Muhammad's death in 632.  The four Rashidun caliphs, who directly succeeded Muhammad as leaders of the Muslim community, were chosen through shura, a process of community consultation that some consider to be an early form of Islamic democracy.  The fourth caliph, Ali, who, unlike the prior three, was from the same clan as Muhammad (Banu Hashim), is considered by Shia Muslims to be the first rightful caliph and Imam after Muhammad.  Ali reigned during the First Fitna (656–661), a civil war between supporters of Ali and supporters of the assassinated previous caliph, Uthman, from Banu Umayya, as well as rebels in Egypt; the war led to the establishment of the Umayyad Caliphate under Muawiyah I in 661.
The second caliphate, the Umayyad Caliphate was ruled by Banu Umayya, a Meccan clan with descent from Muhammad's great-great-grandfather. The caliphate continued the Arab conquests, incorporating the Caucasus, Transoxiana, Sindh, the Maghreb and the Iberian Peninsula (Al-Andalus) into the Muslim world. The caliphate had considerable acceptance of the Christians within its territory, necessitated by their large numbers, especially in the region of Syria.    Following the Abbasid Revolution from 746–750, which primarily arose from non- Arab Muslim disenfranchisement, the Abbasid Caliphate was established in 750.
The third caliphate, the Abbasid Caliphate was ruled by the Abbasids, a dynasty of Meccan origin which descended from Hashim, a great-grandfather of Muhammad, making them part of Banu Hashim, via Abbas, an uncle of Muhammad, hence the name. Caliph al-Mansur founded its second capital of Baghdad in 762 which became a major scientific, cultural and art centre, as did the territory as a whole during a period known as the Islamic Golden Age. From the 10th century, Abbasid rule became confined to an area around Baghdad. From 945 to 1157, the Abbasid Caliphate came under Buyid and then Seljuq military control. In 1250, a non-Arab army created by the Abbasids called the Mamluks came to power in Egypt. In 1258, the Mongol Empire sacked Baghdad, ending the Abbasid Caliphate, and in 1261 the Mamluks in Egypt re-established the Abbasid Caliphate in Cairo. Though lacking in political power, the Abbasid dynasty continued to claim authority in religious matters until the Ottoman conquest of Mamluk Egypt in 1517.
The fourth major caliphate, the Ottoman Caliphate, was established after their conquest of Mamluk Egypt in 1517. The conquest gave the Ottomans control over the holy cities of Mecca and Medina, previously controlled by the Mamluks. The Ottomans gradually came to be viewed as the de facto leaders and representatives of the Islamic world.  Following their defeat in World War I, their empire was partitioned by Britain and France, and on 3 March 1924, the first President of the Turkish Republic, Mustafa Kemal Atatürk, as part of his reforms, constitutionally abolished the institution of the caliphate.  A few other states that existed through history have called themselves caliphates, including the Ismaili Shia Fatimid Caliphate in Northeast Africa (909–1171), the Umayyad Caliphate of Córdoba in Iberia (929–1031), the Berber Almohad Caliphate in Morocco (1121–1269) and the Fula Sokoto Caliphate in present-day northern Nigeria (1804–1903).
The Sunni branch of Islam stipulates that, as a head of state, a caliph should be elected by Muslims or their representatives.  Followers of Shia Islam, however, believe a caliph should be an Imam chosen by God from the Ahl al-Bayt (the "Family of the House", Muhammad's direct descendants). In simpler terms, the Sunni favour election while the Shia favour bloodline. 
The term caliph (/ˈkeɪlɪf, ˈkælɪf/ ),  derives from the Arabic word khalīfah (خَليفة, ), which means "successor", "steward", or "deputy" and has traditionally been considered a shortening of Khalifat Rasul Allah ("successor of the messenger of God"). However, studies of pre-Islamic texts suggest that the original meaning of the phrase was "successor selected by God".
Rashidun Caliphate (632–661)
Succession to Muhammad
In his book The Early Islamic Conquests (1981), Fred Donner argues that the standard Arabian practice at the time was for the prominent men of a kinship group, or tribe, to gather after a leader's death and elect a leader from amongst themselves. There was no specified procedure for this shura or consultation. Candidates were usually, but not necessarily, from the same lineage as the deceased leader. Capable men who would lead well were preferred over an ineffectual heir.
The Shia believe that Ali, the son-in-law and cousin of Muhammad, was chosen by Muhammad as his spiritual and temporal successor as the Mawla (the Imam and the Caliph) of all Muslims in the event of Ghadir Khumm. Here Mohammad called upon the around 100,000 gathered returning pilgrims to give their bay'ah (oath of allegiance) to Ali in his very presence and thenceforth to proclaim the good news of Ali's succession to his (Muhammad's) leadership to all Muslims they should come across.
The caliph was often known as Amir al-Mu'minin (Arabic: أمير المؤمنين "Commander of the Believers"). Muhammad established his capital in Medina; after he died, it remained the capital during the Rashidun Caliphate, before Kufa was reportedly made the capital by Caliph Ali. At times there have been rival claimant caliphs in different parts of the Islamic world, and divisions between the Shi'i and Sunni communities.
According to Sunni Muslims, the first caliph to be called Amir al-Mu'minin was Abu Bakr, followed by Umar, the second of the Rashidun. Uthman and Ali also were called by the same title, while the Shi'a consider Ali to have been the only truly legitimate caliph, of these four men. 
After the first four caliphs, the Caliphate was claimed by the Umayyad Caliphate, the Abbasid Caliphate, and the Ottoman Empire, and for relatively short periods by other, competing dynasties in al-Andalus, North Africa, and Egypt. After the collapse of the Ottoman Empire, Mustafa Kemal Atatürk officially abolished the system of Caliphate in Islam (the Ottoman Empire) as part of his secular reforms and founded the Republic of Turkey in 1923. The Kings of Morocco still label themselves with the title Amir al-Mu'minin for the Moroccans, but lay no claim to the Caliphate.
Some Muslim countries, including Somalia, Indonesia and Malaysia, were never subject to the authority of a Caliphate, with the exception of Aceh, which briefly acknowledged Ottoman suzerainty. Consequently, these countries had their own, local sultans or rulers who did not fully accept the authority of the Caliph.
Abu Bakr, the first successor of Muhammad, nominated Umar as his successor on his deathbed. Umar, the second caliph, was killed by a Persian named Piruz Nahavandi. His successor, Uthman, was elected by a council of electors (majlis). Uthman was killed by members of a disaffected group. Ali then took control but was not universally accepted as caliph by the governors of Egypt, and later by some of his own guard. He faced two major rebellions and was assassinated by Abd-al-Rahman ibn Muljam, a Khawarij. Ali's tumultuous rule lasted only five years. This period is known as the Fitna, or the first Islamic civil war. The followers of Ali later became the Shi'a ("shiaat Ali", partisans of Ali. ) minority sect of Islam and reject the legitimacy of the first 3 caliphs. The followers of all four Rashidun Caliphs (Abu Bakr, Umar, Uthman and Ali) became the majority Sunni sect.
Under the Rashidun each region (Sultanate, Wilayah, or Emirate) of the Caliphate had its own governor (Sultan, Wāli or Emir). Muawiyah, a relative of Uthman and governor (Wali) of Syria, succeeded Ali as Caliph. Muawiyah transformed the caliphate into a hereditary office, thus founding the Umayyad dynasty.
In areas which were previously under Sasanian Empire or Byzantine rule, the Caliphs lowered taxes, provided greater local autonomy (to their delegated governors), greater religious freedom for Jews, and some indigenous Christians, and brought peace to peoples demoralized and disaffected by the casualties and heavy taxation that resulted from the decades of Byzantine-Persian warfare.
Ali's caliphate and the rise of the Umayyad dynasty
Ali's reign was plagued by great turmoil and internal strife. The primary one came from a misunderstanding on the part of Mu'awiyah, the governor of Damascus. The Persians, taking advantage of this, infiltrated the two armies and attacked the other army causing chaos and internal hatred between the companions at the Battle of Siffin. The battle lasted several months, resulting in a stalemate. In order to avoid further bloodshed, Ali agreed to negotiate with Mu'awiyah. This caused a faction of approximately 4,000 people that would be known as the Kharijites, to abandon the fight. After defeating the Kharijites at the Battle of Nahrawan, Ali was later assassinated by the Kharijite Ibn Muljam. Ali's son Hasan was elected as the next caliph, but handed his title to Mu'awiyah a few months later. Mu'awiyah became the fifth (or second by Shia reckoning) caliph, establishing the Umayyad Dynasty,  named after the great-grandfather of Uthman and Mu'awiyah, Umayya ibn Abd Shams. 
Umayyad Caliphate (661–750)
Beginning with the Umayyads, the title of the caliph became hereditary.  Under the Umayyads, the Caliphate grew rapidly in territory, incorporating the Caucasus, Transoxiana, Sindh, the Maghreb and most of the Iberian Peninsula (Al-Andalus) into the Muslim world. At its greatest extent, the Umayyad Caliphate covered 5.17 million square miles (13,400,000 km 2 ), making it the largest empire the world had yet seen, and the sixth-largest ever to exist in history.
Geographically, the empire was divided into several provinces, the borders of which changed numerous times during the Umayyad reign. Each province had a governor appointed by the caliph. However, for a variety of reasons, including that they were not elected by Shura and suggestions of impious behaviour, the Umayyad dynasty was not universally supported within the Muslim community. Some supported prominent early Muslims like Al-Zubayr; others felt that only members of Muhammad's clan, the Banu Hashim, or his own lineage, the descendants of Ali, should rule.
There were numerous rebellions against the Umayyads, as well as splits within the Umayyad ranks (notably, the rivalry between Yaman and Qays). Allegedly, Shimr Ibn Thil-Jawshan killed Ali's son Hussein and his family at the Battle of Karbala in 680, solidifying the Shia-Sunni split.  Eventually, supporters of the Banu Hashim and the supporters of the lineage of Ali united to bring down the Umayyads in 750. However, the Shi‘at ‘Alī, "the Party of Ali", were again disappointed when the Abbasid dynasty took power, as the Abbasids were descended from Muhammad's uncle, ‘Abbas ibn ‘Abd al-Muttalib and not from Ali.
Abbasid Caliphate (750–1258, 1261–1517)
Abbasid Caliphs at Baghdad
In 750, the Umayyad dynasty was overthrown by another family of Meccan origin, the Abbasids. Their time was marked by scientific, cultural and religious prosperity. Islamic art and music also flourished significantly during their reign. Their major city and capital Baghdad began to flourish as a center of knowledge, culture and trade. This period of cultural fruition ended in 1258 with the sack of Baghdad by the Mongols under Hulagu Khan. The Abbasid Caliphate had however lost its effective power outside Iraq already by c. 920.  By 945, the loss of power became official when the Buyids conquered Baghdad and all of Iraq. The empire fell apart and its parts were ruled for the next century by local dynasties. 
In the 9th century, the Abbasids created an army loyal only to their caliphate, composed predominantly of Turkic Cuman, Circassian, and Georgian slave origin known as Mamluks. By 1250 the Mamluks came to power in Egypt. The Mamluk army, though often viewed negatively, both helped and hurt the caliphate. Early on, it provided the government with a stable force to address domestic and foreign problems. However, creation of this foreign army and al-Mu'tasim's transfer of the capital from Baghdad to Samarra created a division between the caliphate and the peoples they claimed to rule. In addition, the power of the Mamluks steadily grew until Ar-Radi (934–41) was constrained to hand over most of the royal functions to Muhammad ibn Ra'iq.
Under the Mamluk Sultanate of Cairo (1261–1517)
In 1261, following the devastation of Baghdad at the hands of the Mongols, the Mamluk rulers of Egypt tried to gain legitimacy for their rule by declaring the re-establishment of the Abbasid caliphate in Cairo. The Abbasid caliphs in Egypt had little to no political power; they continued to maintain the symbols of authority, but their sway was confined to religious matters. The first Abbasid caliph of Cairo was Al-Mustansir (r. June–November 1261). The Abbasid caliphate of Cairo lasted until the time of Al-Mutawakkil III, who ruled as caliph from 1508 to 1516, then he was deposed briefly in 1516 by his predecessor Al-Mustamsik, but was restored again to the caliphate in 1517.
The Ottoman Great Sultan Selim I defeated the Mamluk Sultanate, and made Egypt part of the Ottoman Empire in 1517. Al-Mutawakkil III was captured together with his family and transported to Constantinople as a prisoner where he had a ceremonial role. He died in 1543, following his return to Cairo. 
Parallel caliphates to the Abbasids
The Abbasid dynasty lost effective power over much of the Muslim realm by the first half of the tenth century.
The Shiʻa Ubayd Allah al-Mahdi Billah of the Fatimid dynasty, which claimed descent from Muhammad through his daughter, claimed the title of Caliph in 909, creating a separate line of caliphs in North Africa. Initially controlling Algeria, Tunisia and Libya, the Fatimid caliphs extended their rule for the next 150 years, taking Egypt and Palestine, before the Abbasid dynasty was able to turn the tide, limiting Fatimid rule to Egypt. The Fatimid dynasty finally ended in 1171.
The Umayyad dynasty, which had survived and come to rule over Al-Andalus, reclaimed the title of Caliph in 929, lasting until it was overthrown in 1031.
Fatimid Caliphate (909–1171)
The Fatimid Caliphate was an Isma'ili Shi'i caliphate that spanned a vast area of the Arab world. Originally based in Tunisia, the Fatimid dynasty extended their rule across the Mediterranean coast of Africa, and ultimately made Egypt the centre of their caliphate. At its height, in addition to Egypt, the caliphate included varying areas of the Maghreb, Sicily, the Levant and the Hejaz.
The Fatimids established the Tunisian city of Mahdia and made it their capital city, before conquering Egypt, and building the city of Cairo there in 969. Thereafter, Cairo became the capital of the caliphate, with Egypt becoming the political, cultural and religious centre of the state. Islam scholar Louis Massignon dubbed the 4th century AH /10th century CE as the " Ismaili century in the history of Islam". 
The term Fatimite is sometimes used to refer to the citizens of this caliphate. The ruling elite of the state belonged to the Ismaili branch of Shi'ism. The leaders of the dynasty were Ismaili Imams and had a religious significance to Ismaili Muslims. They are also part of the chain of holders of the office of the Caliphate, as recognized by some Muslims. Therefore, this constitutes a rare period in history in which the descendants of Ali (hence the name Fatimid, referring to Ali's wife Fatima) and the Caliphate were united to any degree, excepting the final period of the Rashidun Caliphate under Ali himself.
Umayyad Caliphate of Córdoba (929–1031)
During the Umayyad dynasty, the Iberian Peninsula was an integral province of the Umayyad Caliphate ruling from Damascus. The Umayyads lost the position of Caliph in Damascus in 750, and Abd al-Rahman I became Emir of Córdoba in 756 after six years in exile. Intent on regaining power, he defeated the existing Islamic rulers of the area who defied Umayyad rule and united various local fiefdoms into an emirate.
Rulers of the emirate used the title "emir" or "sultan" until the 10th century, when Abd al-Rahman III was faced with the threat of invasion by the Fatimid Caliphate. To aid his fight against the invading Fatimids, who claimed the caliphate in opposition to the generally recognized Abbasid Caliph of Baghdad, Al-Mu'tadid, Abd al-Rahman III claimed the title of caliph himself. This helped Abd al-Rahman III gain prestige with his subjects, and the title was retained after the Fatimids were repulsed. The rule of the Caliphate is considered as the heyday of Muslim presence in the Iberian peninsula, before it fragmented into various taifas in the 11th century. This period was characterized by a remarkable flourishing in technology, trade and culture; many of the masterpieces of al-Andalus were constructed in this period.
Almohad Caliphate (1147–1269)
The Almohad movement was started by Ibn Tumart among the Masmuda tribes of southern Morocco. The Almohads first established a Berber state in Tinmel in the Atlas Mountains in roughly 1120.  The Almohads succeeded in overthrowing the Almoravid dynasty in governing Morocco by 1147, when Abd al-Mu'min (r. 1130-1163) conquered Marrakech and declared himself Caliph. They then extended their power over all of the Maghreb by 1159. Al-Andalus followed the fate of Africa and all Islamic Iberia was under Almohad rule by 1172. 
The Almohad dominance of Iberia continued until 1212, when Muhammad al-Nasir (1199–1214) was defeated at the Battle of Las Navas de Tolosa in the Sierra Morena by an alliance of the Christian princes of Castile, Aragon, Navarre and Portugal. Nearly all of the Moorish dominions in Iberia were lost soon after, with the great Moorish cities of Córdoba and Seville falling to the Christians in 1236 and 1248, respectively.
The Almohads continued to rule in northern Africa until the piecemeal loss of territory through the revolt of tribes and districts enabled the rise of their most effective enemies, the Marinid dynasty, in 1215. The last representative of the line, Idris al-Wathiq, was reduced to the possession of Marrakesh, where he was murdered by a slave in 1269; the Marinids seized Marrakesh, ending the Almohad domination of the Western Maghreb.
Ottoman Caliphate (1517–1924)
The caliphate was claimed by the sultans of the Ottoman Empire beginning with Murad I (reigned 1362 to 1389),  while recognizing no authority on the part of the Abbasid caliphs of the Mamluk-ruled Cairo. Hence the seat of the caliphate moved to the Ottoman capital of Edirne. In 1453, after Mehmed the Conqueror's conquest of Constantinople, the seat of the Ottomans moved to Constantinople, present-day Istanbul. In 1517, the Ottoman sultan Selim I defeated and annexed the Mamluk Sultanate of Cairo into his empire.   Through conquering and unifying Muslim lands, Selim I became the defender of the Holy Cities of Mecca and Medina, which further strengthened the Ottoman claim to the caliphate in the Muslim world. Ottomans gradually came to be viewed as the de facto leaders and representatives of the Islamic world. However, the earlier Ottoman caliphs did not officially bear the title of caliph in their documents of state, inscriptions, or coinage.  It was only in the late eighteenth century that the claim to the caliphate was discovered by the sultans to have a practical use, since it allowed them to counter Russian claims to protect Ottoman Christians with their own claim to protect Muslims under Russian rule.  
According to Barthold, the first time the title of "caliph" was used as a political instead of symbolic religious title by the Ottomans was the Treaty of Küçük Kaynarca with the Russian Empire in 1774, when the Empire retained moral authority on territory whose sovereignty was ceded to the Russian Empire.
The British supported and propagated the view that the Ottomans were Caliphs of Islam among Muslims in British India and the Ottoman Sultans helped the British by issuing pronouncements to the Muslims of India telling them to support British rule from Sultan Ali III and Sultan Abdülmecid I. 
The outcome of the Russo-Turkish War of 1768–74 was disastrous for the Ottomans. Large territories, including those with large Muslim populations, such as Crimea, were lost to the Russian Empire. However, the Ottomans under Abdul Hamid I claimed a diplomatic victory by being allowed to remain the religious leaders of Muslims in the now-independent Crimea as part of the peace treaty; in return Russia became the official protector of Christians in Ottoman territory.
Around 1880 Sultan Abdul Hamid II reasserted the title as a way of countering Russian expansion into Muslim lands. His claim was most fervently accepted by the Muslims of British India. By the eve of World War I, the Ottoman state, despite its weakness relative to Europe, represented the largest and most powerful independent Islamic political entity. The sultan also enjoyed some authority beyond the borders of his shrinking empire as caliph of Muslims in Egypt, India, and Central Asia.
In 1899 John Hay, U.S. Secretary of State, asked the American ambassador to Ottoman Turkey, Oscar Straus, to approach Sultan Abdul Hamid II to use his position as caliph to order the Tausūg people of the Sultanate of Sulu in the Philippines to submit to American suzerainty and American military rule; the Sultan obliged them and wrote the letter which was sent to Sulu via Mecca. As a result, the "Sulu Mohammedans ... refused to join the insurrectionists and had placed themselves under the control of our army, thereby recognizing American sovereignty."   
Abolition of the Caliphate (1924)
After the Armistice of Mudros of October 1918 with the military occupation of Constantinople and Treaty of Versailles (1919), the position of the Ottomans was uncertain. The movement to protect or restore the Ottomans gained force after the Treaty of Sèvres (August 1920) which imposed the partitioning of the Ottoman Empire and gave Greece a powerful position in Anatolia, to the distress of the Turks. They called for help and the movement was the result. The movement had collapsed by late 1922.
On 3 March 1924, the first President of the Turkish Republic, Mustafa Kemal Atatürk, as part of Atatürk's Reforms, constitutionally abolished the institution of the caliphate.  Its powers within Turkey were transferred to the Grand National Assembly of Turkey, the parliament of the newly formed Turkish Republic. The title was then claimed by Hussein bin Ali, Sharif of Mecca of Hejaz, leader of the Arab Revolt, but his kingdom was defeated and annexed by ibn Saud in 1925.
A summit was convened at Cairo in 1926 to discuss the revival of the Caliphate, but most Muslim countries did not participate and no action was taken to implement the summit's resolutions.
Though the title Ameer al-Mumineen was adopted by the King of Morocco and by Mohammed Omar, former head of the Taliban of Afghanistan, neither claimed any legal standing or authority over Muslims outside the borders of their respective countries.
Since the end of the Ottoman Empire, occasional demonstrations have been held calling for the reestablishment of the Caliphate. Organisations which call for the re-establishment of the Caliphate include Hizb ut-Tahrir and the Muslim Brotherhood.
Sokoto Caliphate (1804–1903)
The Sokoto Caliphate was an Islamic state in what is now Nigeria led by Usman dan Fodio. Founded during the Fulani War in the early 19th century, it controlled one of the most powerful empires in sub-Saharan Africa prior to European conquest and colonization. The caliphate remained extant through the colonial period and afterwards, though with reduced power. The current head of the Sokoto Caliphate is Sa'adu Abubakar.
Khilafat Movement (1919–24)
The Khilafat Movement was launched by Muslims in British India in 1920 to defend the Ottoman Caliphate at the end of the First World War and it spread throughout the British colonial territories. It was strong in British India where it formed a rallying point for some Indian Muslims as one of many anti-British Indian political movements. Its leaders included Mohammad Ali Jouhar, his brother Shawkat Ali, and Maulana Abul Kalam Azad, Dr. Mukhtar Ahmed Ansari, Hakim Ajmal Khan and Barrister Muhammad Jan Abbasi. For a time it was supported by Mohandas Karamchand Gandhi, who was a member of the Central Khilafat Committee.   However, the movement lost its momentum after the arrest or flight of its leaders, and a series of offshoots splintered off from the main organization.
Sharifian Caliphate (1924–25)
The Sharifian Caliphate (Arabic: خلافة شريفية ) was an Arab caliphate proclaimed by the Sharifian rulers of Hejaz in 1924, in lieu of the Ottoman Caliphate. The idea of the Sharifian Caliphate had been floating around since at least the 15th century. Toward the end of the 19th century, it started to gain importance due to the decline of the Ottoman Empire, which was heavily defeated in the Russo-Turkish War of 1877–78. There is little evidence, however, that the idea of a Sharifian Caliphate ever gained wide grassroots support in the Middle East or anywhere else for that matter.
Sufi caliphates are not necessarily hereditary. Khalifas are aimed to serve the silsilah in relation to spiritual responsibilities and to propagate the teachings of the tariqa.
Ahmadiyya Caliphate (1908-present)
The Ahmadiyya Muslim Community is an Islamic revivalist movement founded in 1889 by Mirza Ghulam Ahmad of Qadian, India, who claimed to be the promised Messiah and Mahdi, awaited by Muslims. He also claimed to be a follower- prophet subordinate to Muhammad the prophet of Islam. After his death in 1908, his first successor, Hakeem Noor-ud-Din became the caliph of the community and assumed the title of Khalifatul Masih (Successor or Caliph of the Messiah).
Ahmadi Muslims believe that the Ahmadiyya Caliphate established after the passing of the community's founder is the re-establishment of the Rashidun Caliphate.  The Ahmadiyya caliphate has spanned over a century, seen five caliphs and continues to operate under this structure, with the caliph having overall authority for all religious and organizational matters. According to Ahmadiyya thought, it is not essential for a caliph to be the head of a state, rather the religious and organisational significance of the caliphate is emphasised. It is above all a religious office, with the purpose to uphold, strengthen and spread Islam and maintain the high moral standards within the Muslim community established by Muhammad, who was not merely a political leader but primarily a religious leader. The caliphate is understood as a system dealing with the organisation of believers and relating to the administration (nizām) of the Muslim community whether or not it involves a governmental role.  Being based on the 'precepts of Prophethood', the institution of caliphate can therefore, like prophethood, exist and flourish without a state.  If a caliph does happen to bear governmental authority as a head of state, it is incidental and subsidiary in relation to his overall function as caliph which is applicable to believers transnationally and not limited to one particular state or political entity. The system of caliphate in Islam, thus understood, transcends national sovereignty and ethnic divide, forming a universal supra-national entity.   According to Ahmadi Muslims, the caliphate seeks to establish God's authority on earth and the caliph strives to uphold that authority within the community of followers. It is required that the caliph carry out his duties through consultation and taking into consideration the views of the members of the Majlis-ash-Shura (consultative body). However, it is not incumbent upon him to always accept the views and recommendations of the members. The caliph has overall authority for all religious and organisational matters and is bound to decide and act in accordance with the Qur'an and sunnah.
After Hakeem Noor-ud-Din, the first caliph, the title of the Ahmadiyya caliph continued under Mirza Mahmud Ahmad, who led the community for over 50 years. Following him were Mirza Nasir Ahmad and then Mirza Tahir Ahmad who were the third and fourth caliphs respectively. The current caliph is Mirza Masroor Ahmad, who lives in London  with a following of 10 to 20 million in over 200 countries and territories of the world. 
The Quran uses the term khalifa twice. First, in al-Baqara, 30, it refers to God creating humanity as his khalifa on Earth. Second, in Sad, 26, it addresses King David as God's khalifa and reminds him of his obligation to rule with justice. 
In addition, the following excerpt from the Quran, known as the 'Istikhlaf Verse', is used by some to argue for a Quranic basis for Caliphate:
God has promised those of you who have attained to faith and do righteous deeds that, of a certainty, He will make them Khulifa on earth, even as He caused [some of] those who lived before them to become Khulifa; and that, of a certainty, He will firmly establish for them the religion which He has been pleased to bestow on them; and that, of a certainty, He will cause their erstwhile state of fear to be replaced by a sense of security [seeing that] they worship Me [alone], not ascribing divine powers to aught beside Me. But all who, after [having understood] this, choose to deny the truth – it is they, they who are truly iniquitous!" (An-Nur, 55)
In the above verse, the word Khulifa (the plural of Khalifa) has been variously translated as "successors" and "ones who accede to power".
Small subsections of Sunni Islamism argue that to govern a state by Sharia is, by definition, to rule via the Caliphate, and use the following verses to sustain their claim.
So govern between the people by that which God has revealed (Islam), and follow not their vain desires, beware of them in case they seduce you from just some part of that which God has revealed to you— [ Quran ]
O you who believe! Obey God, and obey the messenger and then those among you who are in authority; and if you have a dispute concerning any matter, refer it to God and the messenger's rulings, if you are (in truth) believers in God and the Last Day. That is better and more seemly in the end.— [ Quran ]
Hadhrat Huzaifa narrated that the Messenger of Allah said: Prophethood will remain among you as long as Allah wills. Then Caliphate (Khilafah) on the lines of Prophethood shall commence, and remain as long as Allah wills. Then corrupt/erosive monarchy would take place, and it will remain as long as Allah wills. After that, despotic kingship would emerge, and it will remain as long as Allah wills. Then, the Caliphate (Khilafah) shall come once again based on the precept of Prophethood. 
In the above, the first era of Caliphate is commonly accepted by Muslims to be that of the Rashidun Caliphate.
Nafi'a reported saying:
It has been reported on the authority of Nafi, that 'Abdullah b. Umar paid a visit to Abdullah b. Muti' in the days (when atrocities were perpetrated on the People Of Medina) at Harra in the time of Yazid b. Mu'awiya. Ibn Muti' said: Place a pillow for Abu 'Abd al-Rahman (family name of 'Abdullah b. 'Umar). But the latter said: I have not come to sit with you. I have come to you to tell you a tradition I heard from the Messenger of Allah. I heard him say: One who withdraws his band from obedience (to the Amir) will find no argument (in his defence) when he stands before Allah on the Day of Judgment, and one who dies without having bound himself by an oath of allegiance (to an Amir) will die the death of one belonging to the days of Jahiliyyah. – Sahih Muslim, Book 020, Hadith 4562.
Leaders will take charge of you after me, where the pious (one) will lead you with his piety and the impious (one) with his impiety, so only listen to them and obey them in everything which conforms with the truth (Islam). If they act rightly it is for your credit, and if they acted wrongly it is counted for you and against them.
Muslim narrated on the authority of al-A'araj, on the authority of Abu Hurairah, that Muhammad said:
Behold, the Imam (Caliph) is but a shield from behind whom the people fight and by whom they defend themselves.
Muslim reported on the authority of Abdel Aziz al-Muqrin, who said:
I accompanied Abu Hurairah for five years and heard him talking of Muhammd's saying: The Prophets ruled over the children of Israel, whenever a Prophet died another Prophet succeeded him, but there will be no Prophet after me. There will be Khalifahs and they will number many. They asked: What then do you order us? He said: Fulfil the bay'ah(transaction/sale) to them one after the other and give them their due. Surely God will ask them about what He entrusted them with.
Prophesied Caliphate of the Mahdî
Al-Habbab Ibn ul-Munthir said, when the Sahaba met in the wake of the death of Muhammad, (at the thaqifa hall) of Bani Sa’ida:
Let there be one Amir from us and one Amir from you (meaning one from the Ansar and one from the Mohajireen).
Upon this Abu Bakr replied:
It is forbidden for Muslims to have two Amirs (rulers)...
It has additionally been reported  that Abu Bakr went on to say on the day of Al-Saqifa:
It is forbidden for Muslims to have two Amirs for this would cause differences in their affairs and concepts, their unity would be divided and disputes would break out amongst them. The Sunnah would then be abandoned, the bida’a (innovations) would spread and Fitna would grow, and that is in no one’s interests.
The Sahaba agreed to this and selected Abu Bakr as their first Khaleef. Habbab ibn Mundhir who suggested the idea of two Ameers corrected himself and was the first to give Abu Bakr the Bay'ah. This indicates an Ijma as-Sahaba of all of the Sahaba. Ali ibni abi Talib, who was attending the body of Muhammad at the time, also consented to this.
Imam Ali whom the Shia revere said: 
People must have an Amir...where the believer works under his Imara (rule) and under which the unbeliever would also benefit, until his rule ended by the end of his life (ajal ), the booty (fay’i) would be gathered, the enemy would be fought, the routes would be made safe, the strong one will return what he took from the weak till the tyrant would be contained, and not bother anyone.
Sayings of Islamic theologians
It is forbidden for the Ummah (Muslim world) to have two leaders at the same time.
It is forbidden to give an oath to two leaders or more, even in different parts of the world and even if they are far apart.
It is forbidden to appoint two leaders at the same time.
It is permitted to have only one leader (of the Muslims) in the whole of the world.
Al-sha’rani says: 
It is forbidden for Muslims to have in the whole world and at the same time two leaders whether in agreement or discord.
It is forbidden to give the oath to more than one.
Al-Joziri says: 
The Imams (scholars of the four schools of thought)- may Allah have mercy on them- agree that the Caliphate is an obligation, and that the Muslims must appoint a leader who would implement the injunctions of the religion, and give the oppressed justice against the oppressors. It is forbidden for Muslims to have two leaders in the world whether in agreement or discord.
The Shia schools of thought and others expressed the same opinion about this.   However, the Shia school of thought believe that the leader (Imam) must not be appointed by the Islamic ummah, but must be appointed by God.
This Ayah is a source in the selection of an Imaam, and a Khaleef, he is listened to and he is obeyed, for the word is united through him, and the Ahkam (laws) of the Caliph are implemented through him, and there is no difference regarding the obligation of that between the Ummah, nor between the Imams except what is narrated about al-Asam, the Mu'tazzili ...
Al-Qurtubi also said:
The Khilafah is the pillar upon which other pillars rest
(The scholars) consented that it is an obligation upon the Muslims to select a Khalif
Al-Ghazali when writing of the potential consequences of losing the Caliphate said:
The judges will be suspended, the Wilayaat (provinces) will be nullified, ... the decrees of those in authority will not be executed and all the people will be on the verge of Haraam
Ibn Taymiyyah said:
It is obligatory to know that the office in charge of commanding over the people (ie: the post of the Khaleefah) is one of the greatest obligations of the Deen. In fact, there is no establishment of the Deen except by it....this is the opinion of the salaf, such as Al-Fuḍayl ibn ‘Iyāḍ, Ahmad ibn Hanbal and others
Period of dormancy
Once the subject of intense conflict and rivalry amongst Muslim rulers, the caliphate laid dormant and largely unclaimed since the 1920s. For the vast majority of Muslims the caliph as leader of the ummah, "is cherished both as memory and ideal"  as a time when Muslims "enjoyed scientific and military superiority globally".  The Islamic prophet Muhammad is reported to have prophesied:
Prophethood will remain with you for as long as Allah wills it to remain, then Allah will raise it up whenever he wills to raise it up. Afterwards, there will be a Caliphate that follows the guidance of Prophethood remaining with you for as long as Allah wills it to remain. Then, He will raise it up whenever He wills to raise it up. Afterwards, there will be a reign of violently oppressive rule and it will remain with you for as long as Allah wills it to remain. Then, there will be a reign of tyrannical rule and it will remain for as long as Allah wills it to remain. Then, Allah will raise it up whenever He wills to raise it up. Then, there will be a Caliphate that follows the guidance of Prophethood.— As-Silsilah As-Sahihah, vol. 1, no. 5
Islamic State of Iraq and the Levant (2014–present)
The group Tanzim Qaidat al-Jihad fi Bilad al-Rafidayn formed as an affiliate of Al-Qaeda network of Islamist militants during the Iraq War. The group eventually expanded into Syria and rose to prominence as the Islamic State of Iraq and the Levant (ISIL) during the Syrian Civil War. In the summer of 2014, the group launched the Northern Iraq offensive, seizing the city of Mosul.   The group declared itself a caliphate under Abu Bakr al-Baghdadi on 29 June 2014 and renamed itself as the "Islamic State".    ISIL's claim to be the highest authority of Muslims has been widely rejected.  No prominent Muslim scholar has supported its declaration of caliphate; even Salafi-jihadist preachers accused the group of engaging in political showmanship and bringing disrepute to the notion of Islamic state. 
ISIL has been at war with armed forces including the Iraqi Army, the Syrian Army, the Free Syrian Army, Al-Nusra Front, Syrian Democratic Forces, and Iraqi Kurdistan's Peshmerga and People's Protection Units (YPG) along with a 60 nation coalition in its efforts to establish a de facto state on Iraqi and Syrian territory. 
The members of the Ahmadiyya community believe that the Ahmadiyya Caliphate (Arabic: Khilāfah) is the continuation of the Islamic Caliphate, first being the Rāshidūn (rightly guided) Caliphate (of Righteous Caliphs). This is believed to have been suspended with Ali, the son-in-law of Muhammad and re-established with the appearance of Mirza Ghulam Ahmad (1835-1908, the founder of the movement) whom Ahmadis identify as the Promised Messiah and Mahdi.
Ahmadis maintain that in accordance with Quranic verses (such as [ Quran ]) and numerous ahadith on the issue, Khilāfah can only be established by God Himself and is a divine blessing given to those who believe and work righteousness and uphold the unity of God, therefore any movement to establish the Khilāfah centered on human endeavours alone is bound to fail, particularly when the condition of the people diverges from the ‘precepts of prophethood’ and they are as a result disunited, their inability to establish a Khilāfah caused fundamentally by the lack of righteousness in them. Although the khalifa is elected it is believed that God himself directs the hearts of believers towards an individual. Thus the khalifa is designated neither necessarily by right (i.e. the rightful or competent one in the eyes of the people at that time) nor merely by election but primarily by God. 
According to Ahmadiyya thought, a khalifa need not be the head of a state; rather the Ahmadiyya community emphasises the spiritual and organisational significance of the Khilāfah. It is primarily a religious/spiritual office, with the purpose of upholding, strengthening and spreading Islam and of maintaining the high spiritual and moral standards within the global community established by Muhammad - who was not merely a political leader but primarily a religious leader. If a khalifa does happen to bear governmental authority as a head of state, it is incidental and subsidiary in relation to his overall function as khalifa which is applicable to believers transnationally and not limited to one particular state.  
Ahmadi Muslims believe that God has assured them that this Caliphate will endure to the end of time, depending on their righteousness and faith in God. The Khalifa provides unity, security, moral direction and progress for the community. It is required that the Khalifa carry out his duties through consultation and taking into consideration the views of the members of the Shura (consultative body). However, it is not incumbent upon him to always accept the views and recommendations of the members. The Khalifatul Masih has overall authority for all religious and organisational matters and is bound to decide and act in accordance with the Qur'an and sunnah.
A number of Islamist political parties and mujahideen called for the restoration of the caliphate by uniting Muslim nations, either through political action (e.g., Hizb ut-Tahrir), or through force (e.g., al-Qaeda).  Various Islamist movements gained momentum in recent years with the ultimate aim of establishing a Caliphate. In 2014, ISIL/ISIS made a claim to re-establishing the Caliphate. Those advocating the re-establishment of a Caliphate differed in their methodology and approach. Some were locally oriented, mainstream political parties that had no apparent transnational objectives.
Khilafa means representative. Man, according to Islam is the representative of "people", His (God's) viceregent; that is to say, by virtue of the powers delegated to him, and within the limits prescribed by the Qu'ran and the teaching of the prophet, the caliph is required to exercise Divine authority. 
One transnational group whose ideology was based specifically on restoring the caliphate as a pan-Islamic state is Hizb ut-Tahrir (literally, "Party of Liberation"). It is particularly strong in Central Asia and Europe and is growing in strength in the Arab world. It is based on the claim that Muslims can prove that God exists  and that the Qur'an is the word of God.   Hizb ut-Tahrir's stated strategy is a non-violent political and intellectual struggle.
Al-Qaeda's Caliphate goals
Al-Qaeda has as one of its clearly stated goals the re-establishment of a caliphate.  Its former leader, Osama bin Laden, called for Muslims to "establish the righteous caliphate of our umma".  Al-Qaeda chiefs released a statement in 2005, under which, in what they call "phase five" there will be "an Islamic state, or caliphate".  Al-Qaeda has named its Internet newscast from Iraq "The Voice of the Caliphate".  According to author and Egyptian native Lawrence Wright, Ayman al-Zawahiri, bin Laden's mentor and al-Qaeda's second-in-command until 2011, once "sought to restore the caliphate... which had formally ended in 1924 following the dissolution of the Ottoman Empire but which had not exercised real power since the thirteenth century." Zawahiri believes that once the caliphate is re-established, Egypt would become a rallying point for the rest of the Islamic world, leading the jihad against the West. "Then history would make a new turn, God willing", Zawahiri later wrote, "in the opposite direction against the empire of the United States and the world's Jewish government". 
Scholar Olivier Roy writes that "early on, Islamists replace the concept of the caliphate ... with that of the emir." There were a number of reasons including "that according to the classical authors, a caliph must be a member of the tribe of the Prophet (the Quraysh) ... moreover, caliphs ruled societies that the Islamists do not consider to have been Islamic (the Ottoman Empire)."  This is not the view of the majority of Islamist groups, as both the Muslim Brotherhood and Hizb ut-Tahrir view the Ottoman state as a caliphate.  
Electing or appointing a Caliph
In his book The Early Islamic Conquests (1981), Fred Donner argues that the standard Arabian practice during the early Caliphates was for the prominent men of a kinship group, or tribe, to gather after a leader's death and elect a leader from amongst themselves, although there was no specified procedure for this shura, or consultative assembly. Candidates were usually from the same lineage as the deceased leader, but they were not necessarily his sons. Capable men who would lead well were preferred over an ineffectual direct heir, as there was no basis in the majority Sunni view that the head of state or governor should be chosen based on lineage alone.
Following the death of Muhammad, a meeting took place at Saqifah. At that meeting, Abu Bakr was elected caliph by the Muslim community. Sunni Muslims developed the belief that the caliph is a temporal political ruler, appointed to rule within the bounds of Islamic law (Sharia). The job of adjudicating orthodoxy and Islamic law was left to mujtahids, legal specialists collectively called the Ulama. Many Muslims call the first four caliphs the Rashidun, meaning the Rightly-Guided, because they are believed to have followed the Qur'an and the sunnah (example) of Muhammad.
The Shia believe in the Imamate, a principle by which rulers are Imams who are divinely chosen, infallible, and sinless and must come from the Ahl al-Bayt regardless of majority opinion, shura or election. They claim that before his death, Muhammad had given many indications, in the hadith of the pond of Khumm in particular, that he considered Ali, his cousin and son-in-law, as his successor. For the Twelvers, Ali and his eleven descendants, the twelve Imams, are believed to have been considered, even before their birth, as the only valid Islamic rulers appointed and decreed by God.
After these Twelve Imams, the potential Caliphs, had passed, and in the absence of the possibility of a government headed by their Imams, some Twelvers believe it was necessary that a system of Shi'i Islamic government based on the Guardianship of the Islamic Jurist be developed, due to the need for some form of government, where an Islamic jurist or faqih rules Muslims, suffices. However this idea, developed by the marja' Ayatollah Ruhollah Khomeini and established in Iran, is not universally accepted among the Shia.
Ismailis believe in the Imamate principle mentioned above, but they need not be secular rulers as well.
- The Nizari continue to have a living Imam; the current Imam is the Aga Khan.
- The Taiyabi Ismaili have, since the year 1130, followed the Imam's chief officer, the Dai al-Mutlaq, as they believe the Imams are in a state of hiding.
The Majlis al-Shura (literally "consultative assembly") was a representation of the idea of consultative governance. The importance of this is premised by the following verses of the Qur'an:
- "...those who answer the call of their Lord and establish the prayer; and who conduct their affairs by Shura [are loved by God]." 
- "...consult them (the people) in their affairs. Then when you have taken a decision (from them), put your trust in Allah" 
The majlis is also the means to elect a new caliph.  Al-Mawardi has written that members of the majlis should satisfy three conditions: they must be just, have enough knowledge to distinguish a good caliph from a bad one, and have sufficient wisdom and judgment to select the best caliph. Al-Mawardi also said that in emergencies when there is no caliphate and no majlis, the people themselves should create a majlis and select a list of candidates for caliph; then the majlis should select a caliph from the list of candidates. 
Some Islamist interpretations of the role of the Majlis al-Shura are the following: In an analysis of the shura chapter of the Qur'an, Islamist author Sayyid Qutb argues that Islam only requires the ruler to consult with some of the representatives of the ruled and govern within the context of the Sharia. Taqiuddin al-Nabhani, the founder of a transnational political movement devoted to the revival of the Caliphate, writes that although the Shura is an important part of "the ruling structure" of the Islamic caliphate, "(it is) not one of its pillars", meaning that its neglect would not make a Caliph's rule un-Islamic such as to justify a rebellion. However, the Muslim Brotherhood, the largest Islamic movement in Egypt, has toned down these Islamist views by accepting in principle that in the modern age the Majlis al-Shura is democracy but during its governance of Egypt in 2013, the Muslim Brotherhood did not put that principle into practice.
Accountability of rulers
Al-Mawardi said that if the rulers meet their Islamic responsibilities to the public the people must obey their laws, but a Caliph or ruler who becomes either unjust or severely ineffective must be impeached via the Majlis al-Shura. Al-Juwayni argued that Islam is the goal of the ummah, so any ruler who deviates from this goal must be impeached. Al-Ghazali believed that oppression by a caliph is sufficient grounds for impeachment. Rather than just relying on impeachment, Ibn Hajar al-Asqalani stated that the people have an obligation to rebel if the caliph begins to act with no regard for Islamic law. Ibn Hajar al-Asqalani said that to ignore such a situation is haraam and those who cannot revolt from inside the caliphate should launch a struggle from outside. Al-Asqalani used two ayahs from the Qur'an to justify this:
"...And they (the sinners on qiyama) will say, 'Our Lord! We obeyed our leaders and our chiefs, and they misled us from the right path. Our Lord! Give them (the leaders) double the punishment you give us and curse them with a very great curse'..." 
Islamic lawyers commented that when the rulers refuse to step down after being impeached through the Majlis, becoming dictators through the support of a corrupt army, if the majority is in agreement they have the option to launch a revolution. Many noted that this option is to be exercised only after factoring in the potential cost of life. 
Rule of law
Narrated ‘ Aisha: The people of Quraish worried about the lady from Bani Makhzum who had committed theft. They asked, "Who will intercede for her with Allah's Apostle?" Some said, "No one dare to do so except Usama bin Zaid the beloved one to Allah's Apostle." When Usama spoke about that to Allah's Apostle; Allah's Apostle said: "Do you try to intercede for somebody in a case connected with Allah’s Prescribed Punishments?" Then he got up and delivered a sermon saying, "What destroyed the nations preceding you, was that if a noble amongst them stole, they would forgive him, and if a poor person amongst them stole, they would inflict Allah's Legal punishment on him. By Allah, if Fatima, the daughter of Muhammad (my daughter) stole, I would cut off her hand."
Various Islamic lawyers, however, place multiple conditions and stipulations on the execution of such a law, making it difficult to implement. For example, the poor cannot be penalised for stealing out of poverty, and during a time of drought in the Rashidun caliphate, capital punishment was suspended until the effects of the drought passed. 
Islamic jurists later formulated the concept that all classes were subject to the law of the land, and no person is above the law; officials and private citizens alike have a duty to obey the same law. Furthermore, a Qadi (Islamic judge) was not allowed to discriminate on the grounds of religion, race, colour, kinship or prejudice. In a number of cases, Caliphs had to appear before judges as they prepared to render their verdict. 
According to Noah Feldman, a law professor at Harvard University, the system of legal scholars and jurists responsible for the rule of law was replaced by the codification of Sharia by the Ottoman Empire in the early 19th century: 
During the Muslim Agricultural Revolution, the Caliphate understood that real incentives were needed to increase productivity and wealth and thus enhance tax revenues. A social transformation took place as a result of changing land ownership  giving individuals of any gender, ethnic or religious background the right to buy, sell, mortgage, and inherit land for farming or any other purpose. Signatures were required on contracts for every major financial transaction concerning agriculture, industry, commerce and employment. Copies of the contract were usually kept by both parties involved. 
There are similarities between Islamic economics and leftist or socialist economic policies. Islamic jurists have argued that privatization of the origin of oil, gas, and other fire-producing fuels, agricultural land, and water is forbidden. The principle of public or joint ownership has been drawn by Muslim jurists from the following hadith of Muhammad:
Ibn Abbas reported that the Messenger of Allah said: "All Muslims are partners in three things- in water, herbage and fire." (Narrated in Abu Daud, & Ibn Majah)  Anas added to the above hadith, "Its price is Haram (forbidden)."
Aside from similarities to socialism, early forms of proto- capitalism and free markets were present in the Caliphate, since an early market economy and early form of merchant capitalism developed between the 8th and 12th centuries, which some refer to as "Islamic capitalism". A vigorous monetary economy developed based on the circulation of a stable high-value currency (the dinar) and the integration of previously independent monetary areas. Business techniques and forms of business organization employed during this time included early contracts, bills of exchange, long-distance international trade, early forms of partnership (mufawada) such as limited partnerships (mudaraba ), and early forms of credit, debt, profit, loss, capital (al-mal ), capital accumulation (nama al-mal ), circulating capital, capital expenditure, revenue, cheques, promissory notes, trusts (waqf ), startup companies, savings accounts, transactional accounts, pawning, loaning, exchange rates, bankers, money changers, ledgers, deposits, assignments, the double-entry bookkeeping system, and lawsuits. Organizational enterprises similar to corporations independent from the state also existed in the medieval Islamic world. Many of these concepts were adopted and further advanced in medieval Europe from the 13th century onwards.
Early Islamic law included Zakat (charity), one of the Five Pillars of Islam, since the time of the Rashidun caliph Umar in the 7th century. The taxes (including Zakat and Jizya) collected in the treasury (Bayt al-mal) of an Islamic government were used to provide income for the needy, including the poor, elderly, orphans, widows, and the disabled.
The demographics of medieval Islamic society varied in some significant aspects from other agricultural societies, including a decline in birth rates as well as a change in life expectancy. Other traditional agrarian societies are estimated to have had an average life expectancy of 20 to 25 years, while ancient Rome and medieval Europe are estimated at 20 to 30 years.  The life expectancy of Islamic society diverged from that of other traditional agrarian societies, with several studies on the lifespans of Islamic scholars concluding that members of this occupational group enjoyed a life expectancy between 69 and 75 years. Such studies have given the following estimates for the average lifespans of religious scholars at various times and places: 72.8 years in the Middle East, 69–75 years in 11th century Islamic Spain, 75 years in 12th century Persia, and 59–72 years in 13th century Persia. However, Maya Shatzmiller considers these religious scholars to be a misleading sample who are not representative of the general population. Conrad I. Lawrence estimates the average lifespan in the early Islamic Caliphate to be above 35 years for the general population.
The early Islamic Empire also had the highest literacy rates among pre-modern societies, alongside the city of classical Athens in the 4th century BC,  and later, China after the introduction of printing from the 10th century. One factor for the relatively high literacy rates in the early Islamic Empire was its parent-driven educational marketplace, as the state did not systematically subsidize educational services until the introduction of state funding under Nizam al-Mulk in the 11th century.  Another factor was the diffusion of paper from China, which led to an efflorescence of books and written culture in Islamic society; thus papermaking technology transformed Islamic society (and later, the rest of Afro-Eurasia) from an oral to scribal culture, comparable to the later shifts from scribal to typographic culture, and from typographic culture to the Internet. Other factors include the widespread use of paper books in Islamic society (more so than any other previously existing society), the study and memorization of the Qur'an, flourishing commercial activity, and the emergence of the Maktab and Madrasah educational institutions.
- Rashidun ("Righteously Guided")
- Abu Bakr, first Rashidun Caliph. Subdued rebel tribes in the Ridda wars.
- Umar (Umar ibn al-Khattab), second Rashidun Caliph. During his reign, the Islamic empire expanded to include Egypt, Jerusalem and Persia.
- Uthman Ibn Affan, third Rashidun Caliph. The various written copies of the Qur'an were standardized under his direction. Killed by rebels.
- Ali (Ali ibn Abu Talib), fourth Rashidun Caliph. Considered by Shi'a Muslims however to be the first Imam. His reign was fraught with internal conflict, with Muawiyah ibn Abi Sufyan (Muawiyah I) and Amr ibn al-As controlling the Levant and Egypt regions independently of Ali.
- Hasan ibn Ali, fifth Caliph. Considered as "rightly guided" by several historians. He abdicated his right to the caliphate in favour of Muawiyah I in order to end the potential for ruinous civil war.
- Muawiyah I, first caliph of the Umayyad dynasty. Muawiyah instituted dynastic rule by appointing his son Yazid I as his successor, a trend that would continue through subsequent caliphates.
- Umar ibn Abd al-Aziz (Umar II), Umayyad caliph who is considered one of the finest rulers in Muslim history. He is also considered by some (mainly Sunnis) to be among the "rightly guided" caliphs.
- Harun al-Rashid, Abbasid caliph during whose reign Baghdad became the world's prominent centre of trade, learning, and culture. Harun is the subject of many stories in the famous One Thousand and One Nights.
- Al-Ma'mun, a great Abbasid patron of Islamic philosophy and science.
- Mehmed II, an Ottoman caliph who brought an end to the Byzantine Empire.
- Suleiman the Magnificent, an Ottoman caliph during whose reign the Ottoman Empire reached its zenith.
- Abdul Hamid II, last Ottoman caliph to rule with independent, absolute power.
- Abdülmecid II, last caliph of the Ottoman dynasty. Nominally the 37th Head of the Ottoman dynasty.