Theodore I may refer to:
Patriarch Theodore I of Alexandria, Greek Patriarch of Alexandria (607–609) Pope Theodore I (died 649) Theodore I Calliopas, Exarch of Ravenna (643–645 and 653 – c. 666) Patriarch Theodore I of Constantinople (ruled 677–679) Theodore I Laskaris, Emperor of Nicaea (1204–1221 or 1205–1222) Teodor I Muzaka, Albanian despot Theodore I Palaiologos, Despot of the Morea in 1383-1407 Tewodros I of Ethiopia, Emperor of Ethiopia (1413–1414), sometimes known as Theodore I Feodor I of Russia, Tsar of Russia, 1584–1598 Theodore I of Corsica, King of Corsica (1736)