Tsar (/zɑːr, sɑːr/ or /tsɑːr/; Old Church Slavonic: ц︢рь [usually written thus with a title] or цар, царь), also spelled csar, or tzar or czar, is a title used to designate East and South Slavic monarchs or supreme rulers of Eastern Europe, originally Bulgarian monarchs from 10th century onwards. As a system of government in the Tsardom of Russia and the Russian Empire, it is known as Tsarist autocracy, or Tsarism. The term is derived from the Latin word Caesar, which was intended to mean "Emperor" in the European medieval sense of the term—a ruler with the same rank as a Roman emperor, holding it by the approval of another emperor or a supreme ecclesiastical official (the Pope or the Ecumenical Patriarch)—but was usually considered by western Europeans to be equivalent to king, or to be somewhat in between a royal and imperial rank.

"Tsar" and its variants were the official titles of the following states:

The first ruler to adopt the title tsar was Simeon I of Bulgaria.^[2] Simeon II, the last Tsar of Bulgaria, is the last person to have borne the title Tsar.

The title Tsar is derived from the Latin title for the Roman emperors, Caesar.^[3] In comparison to the corresponding Latin word "imperator", the Byzantine Greek term basileus was used differently depending on whether it was in a contemporary political context or in a historical or Biblical context. In the history of the Greek language, basileus had originally meant something like "potentate". It gradually approached the meaning of "king" in the Hellenistic Period, and it came to designate "emperor" after the inception in the Roman Empire. As a consequence, Byzantine sources continued to call the Biblical and ancient kings "basileus" even when that word had come to mean "emperor" when referring to contemporary monarchs (while it was never applied to Western European kings, whose title was transliterated from Latin "rex" as ῥήξ, or to other monarchs, for whom designations such as ἄρχων "leader", "chieftain" were used).

As the Greek "basileus" was consistently rendered as "tsar" in Slavonic translations of Greek texts, the dual meaning was transferred into Church Slavonic. Thus, "tsar" was not only used as an equivalent of Latin "imperator" (in reference to the rulers of the Byzantine Empire, the Holy Roman Empire and to native rulers) but was also used to refer to Biblical rulers and ancient kings.

From this ambiguity, the development has moved in different directions in the different Slavic languages.

Thus, the Bulgarian language and Russian language no longer use tsar as an equivalent of the term emperor/imperator as it exists in the West European (Latin) tradition. Currently, the term tsar refers to native sovereigns, ancient and Biblical rulers, as well as monarchs in fairy tales and the like. The title of king (Russian '*, Bulgarian kral- the origin of which is Charlemagne (Karl)) is sometimes perceived as alien and is by some Russian-speakers reserved for (West) European royalty (and, by extension, for those modern monarchs outside of Europe whose titles are translated as king in English, roi in French etc.). Foreign monarchs of imperial status, both inside and outside of Europe, ancient as well as modern, are generally called imperator (император), rather than tsar.

In contrast, the Serbocroatian language (which can also be viewed as different languages—Serbian, Croatian and Bosnian) translate "emperor" (Latin imperator) as tsar (car, цар) and not as imperator, whereas the equivalent of king (kralj, краљ, король) is used to designate monarchs of non-imperial status, Serbian as well as foreign ancient rulers—like Latin "rex". Biblical rulers in Serbian are called цар and in Croatian kralj.

In the modern West Slavic languages and Slovene language, the use of the terms is nearly identical to the one in English and German: a king is designated with one term (Czech král, Slovak kráľ, Polish król, Slovene kralj), an emperor is designated with another, derived from Caesar as in German (Czech císař, Slovak cisár, Polish cesarz, Slovene cesar; Croatian cesar and Montenegrin ćesar fell into disuse after World War I), while the exotic term "tsar" (Czech, Slovene and Polish car, Slovak cár) is reserved for the Bulgarian, Russian and Serbian rulers.

In the Polish language however tsar is used as an equivalent to imperator, never as king. The term tsar is always used to refer to the Russian rulers before Peter the Great, and very often to those succeeding.

In 705 Emperor Justinian II named Tervel of Bulgaria "Caesar", the first foreigner to receive this title, but his descendants continued to use Bulgar title "Kanasubigi". The sainted Boris I is sometimes retrospectively referred to as tsar, because at his time Bulgaria was converted to Christianity. However, the title "tsar" (and its Byzantine Greek equivalent "basileus") was actually adopted and used for the first time by his son Simeon I, following a makeshift imperial coronation performed by the Patriarch of Constantinople in 913. After an attempt by the Byzantine Empire to revoke this major diplomatic concession and a decade of intensive warfare, the imperial title of the Bulgarian ruler was recognized by the Byzantine government in 924 and again at the formal conclusion of peace in 927. Since in Byzantine political theory there was place for only two emperors, Eastern and Western (as in the Late Roman Empire), the Bulgarian ruler was crowned basileus as "a spiritual son" of the Byzantine basileus.^[5]

Some of the earliest attested occurrences of the titlo-contraction "tsar" (car') from "tsesar" (cěsar') are found in the grave inscription of the chărgubilja (ichirgu-boil) Mostich, a contemporary of Simeon I and Peter I, from Preslav.

It has been hypothesized that Simeon's title was also recognized by a papal mission to Bulgaria in or shortly after 925, as a concession in exchange for a settlement in the Bulgarian-Croatian conflict or a possible attempt to return Bulgaria to union with Rome. Thus, in the later diplomatic correspondence conducted in 1199–1204 between the Bulgarian ruler Kaloyan and Pope Innocent III, Kaloyan—whose self-assumed Latin title was "imperator Bulgarorum et Blachorum"—claims that the imperial crowns of Simeon I, his son Peter I, and of Samuel were somehow derived from the Papacy. The Pope, however, only speaks of reges, kings of Bulgaria in his replies, and eventually grants only that lesser title to Kaloyan, who nevertheless proceeds to thank the Pope for the "imperial title" conferred upon him.^[6]

The title, later augmented with epithets and titles such as autocrat to reflect current Byzantine practice, was used by all of Simeon's successors until the complete conquest of Bulgaria by the Ottoman Empire in 1422. In Latin sources the Emperor of Bulgaria is sometimes designated "Emperor of Zagora" (with variant spellings). Various additional epithets and descriptions apart, the official style read "Emperor and autocrat of all Bulgarians and Greeks".

During the five-century period of Ottoman rule in Bulgaria, the sultan was frequently referred to as "tsar". This may be related to the fact that he had claimed the legacy of the Byzantine Empire or to the fact that the sultan was called "Basileus" in medieval Greek.

After Bulgaria's liberation from the Ottomans in 1878, its new monarchs were at first autonomous prince (knyaz). With the declaration of full independence, Ferdinand I of Bulgaria adopted the traditional title "tsar" in 1908 and it was used until the abolition of the monarchy in 1946. However, these titles were not generally perceived as equivalents of "emperor" any longer. In the Bulgarian as in the Greek vernacular, the meaning of the title had shifted^[7] (although Paisius' Slavonic-Bulgarian History (1760–1762) had still distinguished between the two concepts). Accordingly, while Ferdinand and his successors, Boris III and Simeon II, used the title of "tsar" in Bulgarian, they used the title of "king" outside Bulgaria. In the same fashion, the modern rulers of Greece (1821-1923, 1935-1973) used the traditional title of basileus in Greek and the title of "king" when in English speaking countries.

"Tsar"– was used once by Church officials of Kievan Rus' in the naming of Yaroslav the Wise of Kiev. This may be connected to Yaroslav's war against Byzantium and to his efforts to distance himself from Constantinople. However, other princes of Kievan Rus' never styled themselves as "czars".^[8] Russian lands used the term Tsar from 1547 up when Knyaz (Russian: Князь**)** Ivan IV the Terrible was officially crowned “tsar of all Russia".^[9]

The title of tsar (sr. "car") was used officially by two monarchs, the previous monarchial title being that of king (kralj). In 1345, Stefan Dušan began to style himself "Emperor of Serbs and Greeks" (the Greek renderings read "basileus and autokrator of Serbs and Romans"), and was crowned as such in Skopje on Easter (April 16) 1346 by the newly elevated Serbian patriarch, alongside the Bulgarian patriarch and archbishop of Ohrid. On the same occasion, he had his wife Helena of Bulgaria crowned as empress and his son associated in power as king. When Dušan died in 1355, his son Stefan Uroš V became the next emperor. The new emperor's uncle Simeon Uroš (Siniša) contested the succession and claimed the same titles as a dynast in Thessaly. After his death around 1370, he was succeeded in his claims by his son John Uroš, who retired to a monastery in about 1373.

With the extinction of the Nemanjić dynasty in Serbia in 1371, the imperial title became obsolete (though it was retained by Stefan Uroš IV's widow Elena of Bulgaria until her death in 1376/1377).

The royal title was preserved by Vukašin Mrnjavčević, a Serbian ruler in Macedonia, who had been associated by Stefan Uroš. Several other Serbian rulers are known as tsars, although they were never recognized as such. These include Tsar Lazar (who was titled autokrator), Tsar Jovan Nenad (self-given) and Tsar Stephen the Little (who claimed to be the Russian Emperor in Montenegro).

During the period of the Ottoman rule in Serbia the sultan was also frequently referred to as tsar, for instance in Serbian epic poetry.

The first Russian ruler to openly break with the khan of the Golden Horde, Mikhail of Tver, assumed the title of "Basileus of Rus" and "czar" more commonly spelled "tsar".^[10]

Following his assertion of independence from the khan, "Veliki Kniaz" Ivan III of Muscovy started to use the title of tsar Russian: Царь regularly in diplomatic relations with the West. From about 1480, he is designated as "imperator" in his Latin correspondence, as "keyser" in his correspondence with the Swedish regent, as "kejser" in his correspondence with the Danish king, Teutonic Knights, and the Hanseatic League. Ivan's son Vasily III continued using these titles. Sigismund von Herberstein observed that the titles of "kaiser" and "imperator" were attempts to render the Russian term "tsar" into German and Latin, respectively.^[11]

This was related to Russia's growing ambitions to become an Orthodox "Third Rome", after the Fall of Constantinople. The Muscovite ruler was recognized as an emperor by Holy Roman Emperor Maximilian I in 1514.^[12][13][14] However, the first Russian ruler to be formally crowned as Tsar of All Rus Russian: Царь Всея Руси) was Ivan IV, until then known as Grand Prince of all the Russias. Some foreign ambassadors—namely, Herberstein (in 1516 and 1525), Daniel Printz a Buchau (in 1576 and 1578) and Just Juel (in 1709)—indicated that the word "tsar" should not be translated as "emperor", because it is applied by Russians to David, Solomon and other Biblical kings, which are simple "reges".^[15] On the other hand, Jacques Margeret, a bodyguard of False Demetrius I, argues that the title of "tsar" is more honorable for Muscovites than "kaiser" or "king" exactly because it was God and not some earthly potentate who ordained to apply it to David, Solomon, and other kings of Israel.^[16] Samuel Collins, a court physician to Tsar Alexis in 1659-66, styled the latter "Great Emperour", commenting that "as for the word Czar, it has so near relation to Cesar... that it may well be granted to signifie Emperour. The Russians would have it to be an higher title than King, and yet they call David Czar, and our kings, Kirrols, probably from Carolus Quintus, whose history they have among them".^[17]

In 1610 Sigismund III of Poland manipulated his son Władysław IV's election as tsar of Russia while Polish forces held Moscow during the Time of Troubles following the death of Boris Godunov. His election, which never resulted in his assumption of the Muscovite throne, was part of an unsuccessful plan by Sigismund to conquer all of Russia and convert the population to Catholicism. As a young man Władysław showed ability as a military leader in operations against Muscovy (1617–18) and the Ottoman Empire (1621).^[18]

In 1670, Pope Clement X expressed doubts that it would be appropriate for him to address Alexis as "tsar", because the word is "barbarian" and because it stands for an "emperor", a title reserved for the Holy Roman Emperor. Abbot Scarlati's opined that the term is not translatable and therefore may be used by the Pope without any harm. In order to settle the matter and to assert his imperial ambitions more clearly, Peter I the Great issued an edict that raised Russia to an empire and decreed that the Latin title Imperator should be used instead of Tsar (1721).

The title tsar remained in common usage, and also officially as the designator of various titles signifying rule over various states absorbed by the Muscovite monarchy (such as the former Tatar khanates and the Georgian Orthodox kingdom).

In the 18th century, it was increasingly viewed as inferior to "emperor" or highlighting the oriental side of the term.^[19] Upon annexing Crimea in 1783, Catherine the Great adopted the hellenicized title of Tsaritsa of Tauric Chersonesos, rather than "Tsaritsa of the Crimea". By 1815, when a large part of Poland was annexed, the title had clearly come to be interpreted in Russia as the equivalent of Polish Król "king", and the Russian emperor assumed the title "tsar of Poland".^[20]

Since the word "tsar" remained the popular designation of the Russian ruler despite the official change of style, it is commonly used in foreign languages such as English.

Like many lofty titles, e.g. Mogul, Tsar or Czar has been used as a metaphor for positions of high authority, in English, since 1866 (referring to U.S. President Andrew Johnson), with a connotation of dictatorial powers and style, fitting since "Autocrat" was an official title of the Russian Emperor (informally referred to as 'the Tsar'). Similarly, Speaker of the House Thomas Brackett Reed was called "Czar Reed" for his dictatorial control of the House of Representatives in the 1880s and 1890s.

In the United States and in the UK the title "czar" is a slang term for certain high-level civil servants, such as the "drug czar" for the director of the Office of National Drug Control Policy (not to be confused with a drug baron), "terrorism czar" for a Presidential advisor on terrorism policy, "cybersecurity czar" for the highest-ranking Department of Homeland Security official on computer security and information security policy, and "war czar" to oversee the wars in Iraq and Afghanistan. More specifically, a czar refers to a sub-cabinet-level advisor within the executive branch of the U.S. government. One of the earliest known usages of the term was for Judge Kenesaw Mountain Landis, who was named Commissioner of Baseball, with broad powers to clean up the sport after it had been dirtied by the Black Sox scandal of 1919.^[21]