Emperor of Nicaea (1254-1258), son of Emperor John III Vatatzes (d. 1254) and Irene, daughter of Emperor Theodore I Laskaris, the founder of the Empire of Nicaea. On his accession to the throne, Theodore adopted his mother’s imperial family name.
During Theodore’s short reign, the territorial status quo between the Empire of Nicaea and the Latin Empire of Constantinople remained the same, while two imperial marriages, between his daughters and the new tsar of Bulgaria, Constantine Tich, and the heir of the ruler of Epiros, Nikephoros, appeared to consolidate the Nicaean holdings in Europe. Theodore was a distinguished scholar who wrote essays on theological, philosophical, and scientific topics and composed rhetorical works. He also resumed talks with Rome concerning the reunification of the Greek Orthodox and Latin churches. On his death, at the age of thirty six, he was succeeded by his eight-year-old son John IV.