Ascum (Greek: Ασκούμ) was a general of the Byzantine Empire, active early in the reign of Justinian I (r. 527–565). He was in command of the Praetorian prefecture of Illyricum. His name is reported by John Malalas. Both Theophanes the Confessor and George Kedrenos render his name "Ακούμ" (Acum).
Ascum was reportedly a Hun and a godson of Justinian I. Modern historians consider it likely that the "Huns" of the primary sources were actually Bulgars. Patrick Amory considers the name Ascum to be Germanic in origin. Ascum first appears in 528, already holding the title of stratelates of Illyricum (Greek: ὁ τοῦ 'Ιλλυρικοῦ στρατηλάτης). His title in Latin would be magister militum per Illyricum.
In 528, Ascum joined forces with Constantiolus and Godilas against an invasion force of Huns/Bulgars. Having passed through Scythia (Scythia Minor) and Moesia (Moesia Secunda), the invaders were at the time raiding Thrace. The Byzantine army defeated one group of invaders.
Shortly after their victory, the Byzantine forces were ambushed and routed by a second group of invaders. Both Ascum and Constantiolus were captured in this battle. While Constantiolus was ransomed back to the Byzantines, Ascum "was carried off into captivity". He is not mentioned again and his eventual fate is unknown.
- Martindale, Jones & Morris (1992), p. 136
- Amory, p.484 : "Other Byzantine officers active in the Balkans and bearing Germanic names included Baduarius dux Scythiae, Ascum MVM per Illyricum ... and Chilbudius MVM per Thracias"
- Martindale, Jones & Morris (1992), p. 163-164
- Martindale, Jones & Morris (1992), pp. 748