Kuber (also Kouber or Kuver) was a Bulgar leader who according to the Miracles of Saint Demetrius led in the 670s, a mixed Bulgar and Byzantine Christian population, whose ancestors had been transferred from the Eastern Roman Empire to the Syrmia region in Pannonia by the Avars 60 years earlier. According to a scholarly theory, he was the son of Kubrat, brother of Khan Asparukh and member of the Dulo clan.
Kuber's story was recorded in the second book of the Miracles of Saint Demetrius. The book is a hagiographic work, written in Thessaloniki in the 680s or 690s. According to a scholarly theory, first proposed by the Bulgarian historian Vasil Zlatarski, Kuber was the fourth son of Kubrat, the Christian ruler of the Onogur Bulgars in the steppes north of the Black Sea. Kubrat's (unnamed) fourth son, who left the Pontic steppes after his father's death around 642, became "the subject of the [Khagan] of the Avars in Avar Pannonia and remained there with his army", according to the Byzantine scholar, Theophanes the Confessor. The American historian John Van Antwerp Fine, Jr. writes that, if Zlatarski's theory is correct, Kuber was named after his father, because Kuber and Kubrat are most probably two Greek versions of the same Bulgar name Kurt mentioned in the Nominalia of the Bulgarian khans.