Constantine Doukas of Thessaly

Constantine Doukas (c. 1276–1303) was the second son of John I Doukas, sebastokrator of Thessaly. He succeeded his father around 1289 while still underage, ruling under the regency of Anna Palaiologina Kantakouzene and sharing power with his brother Theodore Angelos until Theodore's death around 1299.

Invested as sebastokrator around 1295, he fought Nikephoros of Epirus and the Angevins, seizing fortresses in 1295 and losing most of them in a 1296 truce. He died in 1303 and was succeeded by his son John II Doukas.