Byzantine ruler of Epiros (c. 1215-1230) and emperor of Thessalonica (1224/1227-1230).
Theodore became second ruler of the autonomous Epirot state on the assassination of his half-brother Michael I. In 1217 he defeated and captured Peter of Courtenay, the Latin emperor of Constantinople; by 1224 he had taken Thessalonica (mod. Thessaloniki, Greece) and extinguished its Latin kingdom. With the capture of Adrianople (mod. Edirne, Turkey) in 1225, Theodore emerged as Nicaea’s chief rival for the restoration of the Byzantine Empire, an aspiration signaled by his coronation as emperor in Thessalonica (c. 1227). However, his ambitions to conquer Constantinople were crushed by Tsar Ivan Asen II of Bulgaria in March 1230 at Klokotnitcha, where he was captured and blinded.
Released from captivity around 1237, Theodore later incited his nephew, Michael II of Epiros (1231-1268/1271), to attack Nicaea (1252-1253). However, the Nicaean emperor John III Doukas Vatatzes defeated the Epirot troops and apprehended Theodore, who was incarcerated in Nicaea and died soon afterward.