Theodosius (Ancient Greek: Θεοδόσιος, romanized: Theodósios; 4 August 583 – shortly after 27 November 602) was the eldest son of Byzantine emperor Maurice (r. 582–602) and was co-emperor from 590 until his deposition and execution during a military revolt.

Sent in an abortive mission to secure aid from Sassanid Persia by his father, Theodosius was said to have been captured and executed by Phocas's supporters a few days after Maurice.

Nevertheless, rumours spread that he had survived the execution, and became popular to the extent that a man who purported to be Theodosius was entertained by the Persians as a pretext for launching a war against Byzantium.

[a] The historian Theophylact Simocatta, the major chronicler of Maurice's reign, also records that on 2 February 602, Germanus saved Theodosius from harm during food riots in Constantinople.

Theodosius promptly informed his father-in-law of this and advised him to hide, and on November 21, Germanus fled first to a local church and then to the Hagia Sophia, seeking sanctuary from the Byzantine emperor's emissaries.

[16] In the middle of the night of November 22, as the crowd rioted and turned against Maurice, the emperor and his family and closest associates fled the capital before the advancing rebel army under Phocas, and crossed over to Chalcedon.

The Persian ruler, in turn, used him as a pretext for his own invasion of Byzantium, claiming that it was done in order to avenge the murder of Maurice and his family and place the "rightful" heir Theodosius on the throne.

[26] James Howard-Johnston disputes the identification of this Theodosius as a pretender, arguing that such claims were Roman propaganda and that it is unlikely that both the people of Edessa in 603 and the notables of Theodosiopolis who met him in 608 would have been deceived by an impostor.