Harthama ibn A'yan (died June 816) is 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 plays an important role in the victory of al-Ma'mun in the Abbasid civil war, but is executed at his orders when he protestsagainst the power of the Sahlid family that dominates his court.