Theodosius, or Theodosios (Θεοδόσιος) was a Byzantine and Eastern Roman emperor of the 4th century. He has a complex history with foreign relations regarding the Goths, Sassanids, Armenians, and Sarmatians, but is regarded as a great emperor. Primarily, he is regarded as a champion of Orthodoxy and oversaw the First Council of Constantinople. He issued the Edict of Thessalonica that reinforced the Nicene Christological position.