Theodosius III was the Byzantine emperor from 715 to 717.

Theodosius III or Theodosios III may also refer to:

Theodosius III of Abkhazia, King of the Abkhazians from circa 975 to 978 Theodosius III of Antioch, Patriarch of Antioch during the mid-11th century Pope Theodosius III of Alexandria, Coptic pope between 1294 and 1300