Kormisosh was a ruler of Bulgaria during the 8th century. The Namelist of Bulgarian Rulers states that he belonged to the Ukil (or Vokil) clan and ruled for 17 years. According to the chronology developed by Moskov, Kormisosh would have reigned from 737 to 754. Other chronologies place his reign in 753–756, but cannot be reconciled with the testimony of the "Namelist" (or would require us to assume a long period of co-regency).
The "Namelist" stresses the fact that the accession of Kormisosh represents a change of dynasty, but it remains unclear whether that was done through violence. The reign of Kormisosh inaugurated a prolonged period of war with the Byzantine Empire. The Byzantine Emperor Constantine V Kopronymos had begun to fortify the frontier and started settling Armenians and Syrians in Byzantine Thrace. In response Kormisosh demanded the payment of tribute, perhaps constituting an increase in the traditional payments. Rebuffed, Kormisosh raided into Thrace, reaching the Anastasian Wall stretching between the Black Sea and the Sea of Marmara 40 km in front of Constantinople. Constantine V marched out with his army, defeated the Bulgarians and turned them to flight.