a Turkic people who contributed to the ethnic stock of present-day Bulgarians.
The earliest reliable written records concerning the Proto-Bulgarians date from the fourth century, when the Proto-Bul-garians inhabited the steppes of southeastern Europe and were allies of Byzantium. After their defeat by the Goths in 480, the Proto-Bulgarians ended their alliance with Byzantium, ravaging Thrace in 499 and attacking Byzantium in the sixth century. A federation of Proto-Bulgarian tribes (Great Bulgaria), headed by Kubrat, formed in the first half of the seventh century in the Azov and Lower Volga regions but collapsed during the reign of Constans II (641–68). In the third quarter of the seventh century, under the pressure of the Khazars, some Proto-Bulgarians moved into the Kama and Middle Volga region. Others, led by Asparukh, migrated to southern Bessarabia and later to territories controlled by Byzantium along the right bank of the Danube.