Eustathios (Greek: Εὐστάθιος) was the Byzantine governor (strategos) of the Cibyrrhaeot Theme in ca.
Eustathios is only mentioned by the De Administrando Imperio, a work compiled in the middle of the 10th century by Constantine VII Porphyrogennetos.
Although both were proteges of the powerful logothetes tou dromou, Himerios, Eustathios clashed with Staurakios over their jurisdiction, as the latter held his appointment directly from the emperor and was wont to disregard the instructions of the theoretically superior strategos.
After remonstrances to Emperor Leo VI the Wise, Staurakios was recalled, and his authority transferred to Eustathios.
[1] As Eustathios remained in office until late 912, when he was replaced by Emperor Alexander with the protospatharios Niketas, he is most likely to be identified with the anonymous strategos of the Cibyrrhaeots who was responsible for the equipment of a fleet and crews in preparation for Himerios' great naval expedition in 911, directed against the Emirate of Crete or the coasts of Syria.