Al-Abbas ibn al-Ma'mun (died 838 CE) was an Arab prince and general, the son of the Abbasid Caliph al-Ma'mun (r. 813–833 CE). A distinguished military leader in the Byzantine–Arab Wars, he was passed over in the succession in favour of his uncle al-Mu'tasim (r. 833–842 CE). In 838, he was arrested for his involvement in a failed conspiracy against Mu'tasim, and died in prison.