The Khazars (Hebrew sing. "Kuzari" כוזרי plur. "Kuzarim" כוזרים; Turkish sing. "Hazar" plur. Hazarlar; Russian sing. Хазарин plur. Хазары; Tatar sing Xäzär plur. Xäzärlär; Crimean Tatar: sing. Hazar, plur. Hazarlar; Greek Χαζάροι/Χάζαροι; Persianخزر khazar; Latin "Gazari" or "Cosri") were a semi-nomadic Turkic people from Central Asia, many of whom converted to Judaism. The name 'Khazar' seems to be tied to a Turkic verb form meaning "wandering" ('gezer' in modern Turkish). In the 7th century CE they founded an independent Khaganate in the Northern Caucasus along the Caspian Sea, where over time Judaism became the state religion. At their height, they and their tributaries controlled much of what is today southern Russia, western Kazakhstan, eastern Ukraine, Azerbaijan, large portions of the Caucasus (including Dagestan, Georgia), and the Crimea.
They were important allies of the Byzantine Empire against the Sassanid Empire and later the Caliphate, the Pechenegs, and the Rus'. In later years, however, once Khazaria had become a significant regional power, the Byzantines abandoned the alliance and turned to the Rus' and Pechenegs against the Khazars. In 965, their sovereignty was broken by Sviatoslav I of Kiev, and they became a subject people of Kievan Rus'. Gradually displaced by the Rus, the Kipchaks, and later the conquering Mongol Golden Horde, the Khazars largely disappeared as a culturally-distinct people.
Today, various place names invoking Khazar persist. Indeed, the Caspian Sea, traditionally known as the Hyrcanian Sea and Mazandaran Sea in Persian, came to be known to Iranians as the Khazar Sea as an alternative name.