Kubrat (Greek: Κροβατον, Kούβρατος; Bulgarian: Кубрат [koˈbrat]) was the ruler of the Onogur–Bulgars, credited with establishing the confederation of Old Great Bulgaria in c. 632. His name derived from the Turkic words qobrat — "to gather", or qurt, i.e. "wolf".

In the Nominalia of the Bulgarian khans Kubrat is mentioned as Kurt (Коуртъ), being a member of the Dulo clan and reigning for 60 years having succeeded Gostun of the Ermi clan.

Bulgars were Turkic nomadic people, who participated in the 5th-century Hunnic confederation. Upon Attila's death, the tribes that later formed the Bulgars had retreated east into the Black Sea-Caspian Steppe. The western Bulgar tribes joined the Avar Khaganate, while the eastern Bulgars came under the Western Turkic Khaganate by the end of the 6th century.

Theophanes the Confessor called him "king of the Onogundur Huns". Patriarch Nikephoros I (758–828) called Kubrat "lord of the Onuğundur" and "ruler of the Onuğundur–Bulğars". John of Nikiu (fl. 696) called him "chief of the Huns". D. Hupchick identified Kubrat as "Onogur", P. Golden as "Oğuro-Bulğar", H. J. Kim as "Bulgar Hunnic/Hunnic Bulgar". According to H. J. Kim the Onogundur/Onogur were evidently part of the Bulgar confederation.

Kubrat spent his early life at the Byzantine Empire imperial palace in Constantinople. As the 7th-century Byzantine historian John of Nikiu narrates:

This project is concerned with Kubratos, chief of the Huns [sic], the nephew of Organa, who was baptized in the city of Constantinople, and received into the Christian community in his childhood and had grown up in the imperial palace. And between him and the elder Heraclius great affection and peace had prevailed, and after Heraclius's death he had shown his affection to his sons and his wife Martina because of the kindness [Heraclius] had shown him. And after he had been baptized with life-giving baptism he overcame all the barbarians and heathens through Virtue of holy baptism. Now touching him it is said that he supported the interests of the children of Heraclius and opposed those of Constantine.

Whether he was a child or a young adult during his time in Constantinople is unclear. The exact time of this event is also unknown but probably coincided with the reign of Emperor Heraclius (r. 610–641). His or Organa's conversion to Christianity is placed circa 619 AD. It seems that young Kubrat was part of the pre-planned coalition, initiated by Heraclius or Organa, against the Sasanian–Avar alliance. This coincides with other alliances by Heraclius with steppe peoples, all in the interest of saving Constantinople.

Kubrat, in 635, according to Nikephoros I, "ruler of the Onoğundur–Bulğars, successfully revolted against the Avars and concluded a treaty with Heraclius". The state Old Great Bulgaria (Magna Bulgaria) was formed. Kubrat died "when Konstantinos was in the West", somewhere during the reign of Constans II (641–668).