Theodore I (d. May 14, 649), who was pope November 24, 642 - May 14, 649, is considered a Greek, but was born in Palestine. He was made a cardinal deacon, (possibly around 640) and a full cardinal by Pope John IV.

His election was supported by the Exarch and he was installed on November 24, 642, succeeding the short reign of Pope John IV. The main feature 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. The decree was condemned, but not by Theodore, who died before he could formulate his answer, leaving his successor, Pope Martin I, to face the Imperial anger. Theodore was buried in St. Peter's.