Dagisthaeus (Greek: Δαγισθαῖος, Dagisthaîos) was a 6th-century Eastern Roman military commander, probably of Gothic origin, in the service of the emperor Justinian I. Dagisthaeus was possibly a descendant of the Ostrogothic chieftain Dagistheus. In 548, Dagisthaeus, still a young officer, was magister militum per Armeniam and commanded a force of 7,000 Romans and 1,000 Tzani sent to recapture the Euxine fortress of Petra, in Lazica, from a Sassanid Persian force during the Lazic War. Dagisthaeus put Petra under siege, but, according to the contemporary historian Procopius, acted in an incompetent manner. He was so confident in victory that he wrote to Justinian, indicating what rewards he thought he and his brother deserved. Dagisthaeus failed in his task, however, and had to flee before a