Azerbaijan, republic in western Asia. Azerbaijan is the easternmost country in the South Caucasus (the southern portion of the region of the Caucasus), which occupies the southern part of the isthmus between the Black and Caspian seas. The country is bordered on the north by Russia, on the east by the Caspian Sea, on the south by Iran, on the west by Armenia, and on the northwest by Georgia. Azerbaijan also shares a short border with Turkey through its autonomous exclave of Naxçivan (Nakhichevan), which is separated from the rest of Azerbaijan by a mountainous strip of Armenian territory. Azerbaijan includes the disputed region of Nagorno-Karabakh, a predominantly Armenian-inhabited enclave in western Azerbaijan. In Azeri, the official state language, the country is called Azarbaijchan Respublikasy (Azerbaijan Republic). Baku, a large port city on the Caspian Sea, is Azerbaijan’s capital and largest city.