The Caucasus () or Caucasia (), is a region between the Black Sea and the Caspian Sea, mainly comprising Armenia, Azerbaijan, Georgia, and parts of Southern Russia. The Caucasus Mountains, including the Greater Caucasus range, have historically been considered as a natural barrier between Eastern Europe and Western Asia.

Mount Elbrus in Russia, Europe's highest mountain, is situated in the Western Caucasus. On the southern side, the Lesser Caucasus includes the Javakheti Plateau and the Armenian highlands, part of which is in Turkey.

The Caucasus is divided into the North Caucasus and South Caucasus, although the Western Caucasus also exists as a distinct geographic space within the North Caucasus. The Greater Caucasus mountain range in the north is mostly shared by Russia and Georgia as well as the northernmost parts of Azerbaijan. The Lesser Caucasus mountain range in the south is occupied by several independent states, mostly by Armenia, Azerbaijan, and Georgia, but also extending to parts of northeastern Turkey, northern Iran and the self-proclaimed Republic of Artsakh.

The region is known for its linguistic diversity: aside from Indo-European and Turkic languages, the Kartvelian, Northwest Caucasian, and Northeast Caucasian language families are indigenous to the area.