Harthama ibn A'yan (; died June 816) was a Khurasan-born general and governor of the early Abbasid Caliphate, serving under the caliphs al-Hadi, Harun al-Rashid and al-Ma'mun. He played an important role in the victory of al-Ma'mun in the Abbasid civil war, but was executed at his orders when he protested against the power of the Sahlid family that dominated his court.