Martinus (son of Heraclius)

Martinus (Greek: Μαρτίνος, translit. Martínos) or Marinus (Greek: Μαρίνος, romanized: Marínos; died possibly in 641) was caesar of the Byzantine Empire from c. 639 to 641. Martinus was the fifth son of Emperor Heraclius and Empress Martina, who was Heraclius' second wife and niece. Martinus was elevated to caesar, a junior imperial title that placed him on the line of succession, at some point between 638 and 640 by his father.

Heraclius died on 11 February 641, leaving the Byzantine Empire to Martinus's half-brother Constantine III and his elder full brother Heraclonas; Constantine III soon died of tuberculosis, although some of his partisans alleged that Martina poisoned him. One such partisan, Valentinus, led troops to Chalcedon, across the Bosporus strait from the imperial capital, Constantinople, to force Martina to install Constans II, the son of Constantine III, as co-emperor. Valentinus seized Constantinople and forced Martina to install Constans II in September or October 641, and deposed Martina, Heraclonas, and Martinus. Martinus was mutilated and exiled to Rhodes. He died soon after, possibly during or immediately after the mutilations.