The Khazars (//, /-/; Azerbaijani: Xəzərlər; Turkish: Hazarlar; Bashkir: Хазарлар; Tatar: Хәзәрләр, Xäzärlär; Hebrew: כוזרים, Kuzarim; Arabic: خزر, Xazar; Ukrainian: Хоза́ри, Chozáry; Russian: Хаза́ры, Hazáry; Hungarian: Kazárok; Persian: خزر, Xazar; Greek: Χάζαροι, Cházaroi; Latin: Gazari/Gasani) were a semi-nomadic Turkic people, who created what for its duration was the most powerful polity to emerge from the break-up of the Western Turkic Khaganate. Astride a major artery of commerce between Eastern Europe and Southwestern Asia, Khazaria became one of the foremost trading emporia of the medieval world, commanding the western marches of the Silk Road and playing a key commercial role as a crossroad between China, the Middle East and Kievan Rus'. For some three centuries (c. 650–965) the Khazars dominated the vast area extending from the Volga-Don steppes to the eastern Crimea and the northern Caucasus.
Khazaria long served as a buffer state between the Byzantine Empire and both the nomads of the northern steppes and the Umayyad Caliphate, after serving as Byzantium's proxy against the Sasanian Persian empire. The alliance was dropped around 900. Byzantium began to encourage the Alans to attack Khazaria and weaken its hold on Crimea and the Caucasus, while seeking to obtain an entente with the rising Rus' power to the north, which it aspired to convert to Christianity. Between 965 and 969, the Kievan Rus' ruler Sviatoslav I of Kiev conquered the capital Atil and destroyed the Khazar state.
Determining the origins and nature of the Khazars is closely bound with theories of their languages, but it is a matter of intricate difficulty since no indigenous records in the Khazar language survive, and the state was polyglot and polyethnic. The native religion of the Khazars is thought to have been Tengrism, like that of the North Caucasian Huns and other Turkic peoples. The polyethnic populace of the Khazar Khaganate appears to have been a multiconfessional mosaic of pagan, Tengrist, Jewish, Christian and Muslim worshippers. The ruling elite of the Khazars was said by Judah Halevi and Abraham ibn Daud to have converted to Rabbinic Judaism in the 8th century, but the scope of the conversion within the Khazar Khanate remains uncertain.
Proposals of Khazar origins have been made regarding the Slavic Judaising Subbotniks, the Bukharan Jews, the Muslim Kumyks, Kazakhs, the Cossacks of the Don region, the Turkic-speaking Krymchaks and their Crimean neighbours the Karaites to the Moldavian Csángós, the Mountain Jews and others. In the late 19th century, a theory emerged that the core of today's Ashkenazi Jews descended from a hypothetical Khazarian Jewish diaspora who had migrated westward from modern Russia and Ukraine into modern France and Germany. This theory still finds occasional support, but most scholars view it with scepticism. The theory is sometimes associated with antisemitism and anti-Zionism.
Gyula Németh, following Zoltán Gombocz, derived Xazar from a hypothetical *Qasar reflecting a Turkic root qaz- ("to ramble, to roam") being an hypothetical velar variant of Common Turkic kez-. In the fragmentary Tes and Terkhin inscriptions of the Uyğur empire (744–840) the form 'Qasar' is attested, though uncertainty remains whether this represents a personal or tribal name, gradually other hypotheses emerged. Louis Bazin derived it from Turkic qas- ("tyrannize, oppress, terrorize") on the basis of its phonetic similarity to the Uyğur tribal name, Qasar. András Róna-Tas connects it with Kesar, the Pahlavi transcription of the Roman title Caesar.