The Caucasus /ˈkɔːkəsəs/ or Caucasia /kɔːˈkeɪʒə/ is a region located at the border of Europe and Asia, situated between the Black Sea and the Caspian Sea. It is home to the Caucasus Mountains, which contain Europe's highest mountain, Mount Elbrus, at 5,642 metres (18,510 ft), located on the west of the Greater Caucasus mountain range. The Greater Caucasus mountain range acts as a natural barrier separating Eastern Europe from Western Asia, the latter including the Transcaucasus and Anatolia regions.
The Caucasus region is separated between northern and southern parts – the North Caucasus (Ciscaucasus) and Transcaucasus, respectively. The Greater Caucasus mountain range in the north is within the Russian Federation, while the Lesser Caucasus mountain range in the south is divided between several independent states, namely Georgia, Armenia, Azerbaijan. The Transcaucasus extends eastwards to the Caspian Sea and northwestern Iran, and extends westwards into northeastern Turkey.  
Pliny the Elder's Natural History (77–79 AD) derives the name of the Caucasus from Scythian kroy-khasis ("ice-shining, white with snow"). German linguist Paul Kretschmer notes that the Latvian word Kruvesis also means "ice".
In the Tale of Past Years (1113 AD), it is stated that Old East Slavic Кавкасийскыѣ горы ( Kavkasijskyě gory ) came from Ancient Greek Καύκασος ( Kafkasos ), which, according to M. A. Yuyukin, is a compound word that can be interpreted as the "Seagull's Mountain" (καύ-: καύαξ, καύηξ, ηκος ο, κήξ, κηϋξ "a kind of seagull" + the reconstructed *κάσος η "mountain" or "rock" richly attested both in place and personal names.) 
According to German philologists Otto Schrader and Alfons A. Nehring, the Ancient Greek word Καύκασος ( Kafkasos ) is connected to Gothic Hauhs ("high") as well as Lithuanian Kaũkas ("hillock") and Kaukarà ("hill, top"). British linguist Adrian Room points out that Kau- also means "mountain" in Pelasgian. 
The Transcaucasus region and southern Dagestan were the furthest points of Persian Parthian and later Sasanian expansions, with areas to the north of the Greater Caucasus range practically impregnable. The mythological Mount Qaf, the world's highest mountain that ancient Iranian lore shrouded in mystery, was said to be situated in this region, making the Caucasus the highest limit of the world.
Endonyms and exonyms
The modern name for the region is usually similar in the many languages, and is generally between Kavkaz and Kawkaz .
- Abkhaz: Кавказ Kavkaz
- Adyghe: Къаукъаз/с Kʺaukʺaz/s
- Azerbaijani: Qafqaz
- Arabic: القوقاز al-Qawqāz
- Armenian: Կովկաս Kovkas
- Avar: Кавказ Kawkaz
- Chechen: Кавказ Kavkaz
- Georgian: კავკასია K'avk'asia
- German: Kaukasien
- Greek: Καύκασος Káfkasos
- Hebrew: קווקז Qavqaz
- Ingush: Кавказ Kawkaz
- Karachay-Balkar: Кавказ Kavkaz
- Kurdish: Qefqasya/Qefqas
- Lak: Ккавкказ Kkawkkaz
- Lezgian: Къавкъаз K'awk'az
- Ossetian: Кавказ Kavkaz
- Persian: قفقاز Qafqāz
- Russian: Кавказ Kavkaz
- Rutul: Qawqaz Kavkaz
- Turkish: Kafkaslar/Kafkasya
- Ukrainian: Кавказ Kavkaz
The Ciscaucasus contains most of the Greater Caucasus mountain range. It consists of Southern Russia, mainly the North Caucasian Federal District's autonomous republics, and the northernmost parts of Georgia and Azerbaijan. The Ciscaucasus lies between the Black Sea to its west, the Caspian Sea to its east, and borders the Southern Federal District to its north. The two Federal Districts are collectively referred to as "Southern Russia."
The Transcaucasus borders the Greater Caucasus range and Southern Russia to its north, the Black Sea and Turkey to its west, the Caspian Sea to its east, and Iran to its south. It contains the Lesser Caucasus mountain range and surrounding lowlands. All of Armenia, Azerbaijan (excluding the northernmost parts) and Georgia (excluding the northernmost parts) are in the South Caucasus.
The watershed along the Greater Caucasus range is generally perceived to be the dividing line between Europe and Southwest Asia. The highest peak in the Caucasus is Mount Elbrus (5,642 meters) located in western Ciscaucasus, and is considered as the highest point in Europe.
The Caucasus is one of the most linguistically and culturally diverse regions on Earth. The nation states that comprise the Caucasus today are the post-Soviet states Georgia (including Adjara), Azerbaijan (including Nakhchivan), Armenia, and the Russian Federation. The Russian divisions include Dagestan, Chechnya, Ingushetia, North Ossetia–Alania , Kabardino–Balkaria , Karachay–Cherkessia , Adygea, Krasnodar Krai and Stavropol Krai, in clockwise order.
Three territories in the region claim independence but are recognised as such by only a handful or by no independent UN countries: Artsakh , Abkhazia and South Ossetia. Abkhazia and South Ossetia are recognised by the majority of countries as part of Georgia, and Artsakh as part of Azerbaijan.
The region has many different languages and language families. There are more than 50 ethnic groups living in the region.  No fewer than three language families are unique to the area. In addition, Indo-European languages, such as Armenian and Ossetian, and Turkic languages, such as Azerbaijani and Karachay–Balkar, are spoken in the area. Russian is used as a lingua franca most notably in the North Caucasus.
The peoples of the northern and southern Caucasus tend to be either Sunni Muslims, Eastern Orthodox Christians and Armenian Christians. Twelver Shi'ism has many adherents in the southeastern part of the region, in Azerbaijan which extends into Iran.
Located on the peripheries of Turkey, Iran, and Russia, the region has been an arena for political, military, religious, and cultural rivalries and expansionism for centuries. Throughout its history, the Caucasus was usually incorporated into the Iranian world.  At the beginning of the 19th century, the Russian Empire conquered the territory from Qajar Iran. 
The territory of the Caucasus region was inhabited by Homo erectus since the Paleolithic Era. In 1991, early human (that is, hominin) fossils dating back 1.8 million years were found at the Dmanisi archaeological site in Georgia. Scientists now classify the assemblage of fossil skeletons as the subspecies Homo erectus georgicus . 
The site yields the earliest unequivocal evidence for presence of early humans outside the African continent;  and the Dmanisi skulls are the five oldest hominins ever found outside Africa, thereby doubling the presumed age of the human migration outside the continent. 
Under Ashurbanipal (669–627 BC) the boundaries of the Assyrian Empire reached as far as the Caucasus Mountains. Later ancient kingdoms of the region included Armenia, Albania, Colchis and Iberia, among others. These kingdoms were later incorporated into various Iranian empires, including Media, the Achaemenid Empire, Parthia, and the Sassanid Empire, who would altogether rule the Caucasus for many hundreds of years. In 95–55 BC under the reign of Armenian king of kings Tigranes the Great, the Kingdom of Armenia became an empire, growing to include: Kingdom of Armenia, vassals Iberia, Albania, Parthia, Atropatene, Mesopotamia, Cappadocia, Cilicia, Syria, Nabataean kingdom, and Judea. By the time of the first century BC, Zoroastrianism had become the dominant religion of the region; however, the region would go through two other religious transformations. Owing to the strong rivalry between Persia and Rome, and later Byzantium, the latter would invade the region several times, although it was never able to hold the region.
As the Arsacid dynasty of Armenia (an eponymous branch of the Arsacid dynasty of Parthia) was the first nation to adopt Christianity as state religion (in 301 AD), and Caucasian Albania and Georgia had become Christian entities, Christianity began to overtake Zoroastrianism and pagan beliefs. With the Muslim conquest of Persia, large parts of the region came under the rule of the Arabs, and Islam penetrated into the region.  In the 10th century, the Alans (proto- Ossetians)  founded the Kingdom of Alania, that flourished in the Northern Caucasus, roughly in the location of latter-day Circassia and modern North Ossetia–Alania, until its destruction by the Mongol invasion in 1238–39. In the 12th century, the Georgian king David the Builder drove the Muslims out from Caucasus and made the Kingdom of Georgia a strong regional power. In 1194–1204 Georgian Queen Tamar's armies crushed new Seljuk Turkish invasions from the south-east and south and launched several successful campaigns into Seljuk Turkish-controlled Southern Armenia. The Georgian Kingdom continued military campaigns in the Caucasus region. As a result of her military campaigns and the temporary fall of the Byzantine Empire in 1204, Georgia became the strongest Christian state in the whole Near East area, encompassing most of the Caucasus stretching from Northern Iran and Northeastern Turkey to the North Caucasus. The Caucasus region would later be conquered by the Ottomans, Mongols, local kingdoms and khanates, as well as, once again, Iran.
In the 10th century, the Alans (proto- Ossetians)  founded the Kingdom of Alania in the Northern Caucasus. It was destroyed by the Mongol invasion in 1238–39. Parts of the Southern Caucasus, on the other hand, were under the political domination of Arab rulers for a while. In the 12th century, Georgian king David the Builder drove the Arabs out of the region and made the Kingdom of Georgia a strong regional power. In 1194–1204 Georgian Queen Tamar's armies crushed new Seljuk Turkish invasions from the south-east and south and launched several successful campaigns into Seljuk Turkish-controlled Southern Armenia. The Georgian Kingdom continued military campaigns in the Caucasus region. As a result of her military campaigns and the temporary fall of the Byzantine Empire in 1204, Georgia became one of the strongest Christian states, encompassing most of the southern Caucasus in addition to northeastern Anatolia. The region would later be conquered by the Ottomans, Mongols, Iran as well as local kingdoms and khanates.
Up to including the early 19th century, the Southern Caucasus and southern Dagestan all formed part of the Persian Empire. In 1813 and 1828 by the Treaty of Gulistan and the Treaty of Turkmenchay respectively, the Persians were forced to irrevocably cede the Southern Caucasus and Dagestan to Imperial Russia.  In the ensuing years after these gains, the Russians took the remaining part of the Southern Caucasus, comprising western Georgia, through several wars from the Ottoman Empire.  
In the second half of the 19th century, the Russian Empire also conquered the Northern Caucasus. In the aftermath of the Caucasian Wars, an ethnic cleansing of Circassians was performed by Russia in which the indigenous peoples of this region, mostly Circassians, were expelled from their homeland and forced to move primarily to the Ottoman Empire.  
In the 1940s, around 480,000 Chechens and Ingush, 120,000 Karachay – Balkars and Meskhetian Turks, thousands of Kalmyks, and 200,000 Kurds in Nakchivan and Caucasus Germans were deported en masse to Central Asia and Siberia. About a quarter of them died. 
The Southern Caucasus region was unified as a single political entity twice – during the Russian Civil War ( Transcaucasian Democratic Federative Republic) from 9 April 1918 to 26 May 1918, and under the Soviet rule ( Transcaucasian SFSR) from 12 March 1922 to 5 December 1936. Following the dissolution of the Soviet Union in 1991, Georgia, Azerbaijan and Armenia became independent nations.
The region has been subject to various territorial disputes since the collapse of the Soviet Union, leading to the Nagorno-Karabakh War (1988–1994), the East Prigorodny Conflict (1989–1991), the War in Abkhazia (1992–93), the First Chechen War (1994–1996), the Second Chechen War (1999–2009), and the 2008 South Ossetia War.
In Greek mythology the Caucasus, or Kaukasos, was one of the pillars supporting the world. After presenting man with the gift of fire, Prometheus (or Amirani in Georgian version) was chained there by Zeus, to have his liver eaten daily by an eagle as punishment for defying Zeus' wish to keep the "secret of fire" from humans.
The Roman poet Ovid placed Caucasus in Scythia and depicted it as a cold and stony mountain which was the abode of personified hunger. The Greek hero Jason sailed to the west coast of the Caucasus in pursuit of the Golden Fleece, and there met Medea, a daughter of King Aeëtes of Colchis.
The Caucasus is an area of great ecological importance. The region is included in the list of 34 world biodiversity hotspots.   It harbors some 6400 species of higher plants, 1600 of which are endemic to the region.  Its wildlife includes Persian leopards, brown bears, wolves, bison, marals, golden eagles and hooded crows. Among invertebrates, some 1000 spider species are recorded in the Caucasus.   Most of Arthropod biodiversity is concentrated on Great and Lesser Caucasus ranges.  The region has a high level of endemism and a number of relict animals and plants, the fact reflecting presence of refugial forests, which survived the Ice Age in the Caucasus Mountains. The Caucasus forest refugium is the largest throughout the Western Asian (near Eastern) region.  The area has multiple representatives of disjunct relict groups of plants with the closest relatives in Eastern Asia, southern Europe, and even North America. Over 70 species of forest snails of the region are endemic. Some relict species of vertebrates are Caucasian parsley frog, Caucasian salamander, Robert's snow vole, and Caucasian grouse, and there are almost entirely endemic groups of animals such as lizards of genus Darevskia . In general, species composition of this refugium is quite distinct and differs from that of the other Western Eurasian refugia.  The natural landscape is one of mixed forest, with substantial areas of rocky ground above the treeline. The Caucasus Mountains are also noted for a dog breed, the Caucasian Shepherd Dog (Rus. Kavkazskaya Ovcharka, Geo. Nagazi). Vincent Evans noted that minke whales have been recorded from the Black Sea.