Pope Theodore I (Latin: Theodorus I; died 14 May 649) was Pope from 24 November 642 to his death in 649. Although considered a Greek, he was born in Jerusalem. He was among the many Syrian clergy who fled to Rome following the Muslim conquest of the Levant.
His election was supported by the exarch and he was installed on 24 November 642, succeeding John IV. The main focus of his pontificate was the continued struggle against the heretical Monothelites. He refused to recognize Paul as the Patriarch of Constantinople, because his predecessor, Pyrrhus, had not been correctly replaced. He pressed Emperor Constans II to withdraw the Ecthesis of Heraclius. While his efforts made little impression on Constantinople, it increased the opposition to the heresy in the West; Pyrrhus even briefly recanted his heresy (645), but was excommunicated in 648. Paul was excommunicated in 649. In response, Paul destroyed the Roman altar in the palace of Placidia and exiled or imprisoned the papal nuncios. But he also sought to end the issue with the Emperor by promulgating the Type of Constans, ordering that the Ecthesis be taken down and seeking to end discussion on the doctrine.