| Theodore Komnenos Doukas | |
|---|---|
| Emperor and Autocrat of the Romans Emperor of Thessaloniki Despot of Epirus & Arta | |
 Electrum coin with Theodore (left) blessed by Thessalonica's patron, St. Demetrius | |
| Emperor of Thessalonica Claimant Byzantine Emperor | |
| Reign | 1224–1230 |
| Successor | Manuel Komnenos Doukas |
| Ruler of Epirus | |
| Reign | 1215–1230 |
| Predecessor | Michael I Komnenos Doukas |
| Successor | Michael II Komnenos Doukas |
| Died | c. 1253 |
| Spouse | Maria Petraliphaina |
| Issue | Anna Angelina Komnene Doukaina John Komnenos Doukas Irene Komnene Doukaina Demetrios Angelos Doukas |
| Dynasty | Komnenodoukas branch of the Angelos dynasty |
| Father | John Doukas |
| Mother | Zoe Doukaina |
Theodore Komnenos Doukas (Greek: Θεόδωρος Κομνηνὸς Δούκας, Theodōros Komnēnos Doukas; Latinized as Theodore Comnenus Ducas; died c. 1253) or Theodore Angelos Komnenos was the ruler of Epirus and Thessaly from 1215 to 1230 and of Thessalonica and most of Macedonia and western Thrace from 1224 to 1230. He was also the power behind the rule of his sons John and Demetrios over Thessalonica in 1237–1246.
Theodore was the scion of a distinguished Byzantine aristocratic family related to the imperial Komnenos, Doukas, and Angelos dynasties. Nevertheless, nothing is known about Theodore's life before the conquest of Constantinople and dissolution of the Byzantine Empire by the Fourth Crusade in 1204. Following the fall of Constantinople, he served Theodore I Laskaris, founder of the Empire of Nicaea, for a few years before being called to Epirus, where his half-brother Michael I Komnenos Doukas had founded an independent principality. When Michael died in 1215, Theodore sidelined his brother's underage and illegitimate son Michael II and assumed the governance of the Epirote state. Theodore continued his brother's policy of territorial expansion. Allied with Serbia, he expanded into Macedonia, threatening the Latin Kingdom of Thessalonica. The capture of the Latin Emperor Peter II of Courtenay in 1217 opened the way to the gradual envelopment of Thessalonica, culminating in the city's fall in 1224.
As ruler of Thessalonica, Theodore quickly declared himself emperor, challenging the Nicaean emperor John III Doukas Vatatzes's claims to the Byzantine imperial throne. In 1225, he advanced to the outskirts of Constantinople, but his final attack against the seat of the much-reduced Latin Empire was delayed until 1230. In that year, Theodore amassed an army to besiege Constantinople, but then diverted it against Bulgaria, an ambivalent ally which threatened his northern flank. Theodore was defeated and captured at the Battle of Klokotnitsa, and spent the next seven years in captivity. In the meantime, he was succeeded by his brother Manuel. Manuel quickly lost Thrace, most of Macedonia, and Albania to the Bulgarian Emperor John Asen II. Thessalonica itself became a Bulgarian vassal, while in Epirus proper power was seized by Michael II, returning from exile.
Theodore was released in 1237 when his daughter Irene married John Asen II, and quickly managed to regain control of Thessalonica, ousting Manuel. Having been blinded during his captivity and thus disqualified from occupying the throne again, he installed his eldest son John as emperor, but remained the de facto regent of the state. Manuel tried to regain Thessalonica with Nicaean support, but a negotiated settlement was reached which gave him Thessaly and left Thessalonica and its environs to Theodore and John. In 1241, John III Vatatzes invited Theodore to visit Nicaea. He was welcomed and treated with great honour, but was effectively detained there until the spring of next year, when Vatatzes marched on Thessalonica with Theodore in tow. Theodore was sent in to negotiate with his son and convince him to accept demotion to the rank of Despot and to recognize the suzerainty of Nicaea. John died in 1244 and was succeeded by Theodore's younger son Demetrios. In 1246, Vatatzes overthrew the unpopular Demetrios and annexed Thessalonica. Theodore influenced his nephew Michael II to launch an attack on Thessalonica in 1251, but in 1252, Vatatzes campaigned against them and forced Michael to come to terms. Theodore was taken prisoner and sent into exile in Nicaea, where he died around 1253.