Constantinus Heraclius (Greek: Κωνσταντῖνος Ἡράκλειος), known in English as Heraklonas, Heraclonas, or Heracleonas (626–641), was the son of Heraclius and his niece Martina, and was Byzantine Emperor briefly between February and September 641.

He was baptised and officially reigned as Constantinus Heraclius, but the diminutive nickname Heraklonas (Ἡρακλωνᾶς), little Heraclius, became established in Byzantine texts and has become standard in historiography.

Heraklonas was probably born at Lazica while his father was on campaign against Khosrau II of the Sassanid Empire. He was probably the fourth son of Martina and Herakleios, but the first one born free of physical deformity and eligible for the throne.

Towards the end of Heraclius' reign he obtained through his mother’s influence the title of Augustus on July 4, 638, and after his father’s death was proclaimed joint emperor with his older half-brother Constantine III (Herakleios Constantine).

The premature death of Constantine III, in May 641, left Heraklonas sole ruler. But a suspicion that he and Martina had murdered Constantine led soon after to a revolt under the general Valentinus, who forced Heraklonas to accept his young nephew Constans II as co-ruler. Martina intended to balance this setback with the coronation of her younger son the Caesar David (Tiberios) as emperor.