Muhammad ibn Harun al-Rashid, better known by his regnal name of al-Amin (April 787 – 24/25 September 813) (Arabic: محمد الأمين بن هارون الرشيد‎‎), was the sixth Abbasid Caliph. He succeeded his father, Harun al-Rashid in 809 and ruled until he was deposed and killed in 813, during the civil war with his brother, al-Ma'mun.

Muhammad ibn Jarir al-Tabari records that Harun al-Rashid several times impressed on his sons they should respect each other and honour the succession as Harun arranged it. In A.H. 186, Harun had al-Amin and al-Ma'mun sign pledges during a pilgrimage to Mecca that both would honour his will. Al-Amin, would receive the Caliphate and al-Ma'mun would become governor of Khurasan in eastern Iran and would furthermore be granted almost complete autonomy. On al-Amin's death, according to Harun's decision, al-Ma'mun would become Caliph.

Al-Ma'mun had distrusted al-Amin before their father's death and convinced Harun to take him with him on Harun's last journey east. Although Harun had instructed the Baghdad commanders of this expedition to remain with al-Ma'mun, after Harun's death they returned to Baghdad. Al-Amin sought to turn al-Ma'mun's financial agent in Rayy against al-Ma'mun and he ordered al-Ma'mun to acknowledge al-Amin's son Musa as heir and return to Baghdad. Al-Ma'mun replaced his agent in Rayy and refused the orders. His mother was Persian and he had strong support in Iran.

The brothers had different mothers. Al-Amin was prompted to move against al-Ma'mun by meddlesome ministers, especially al-Fadl ibn al-Rabi'. Al-Amin had Harun's succession documents brought from Mecca to Baghdad, where he destroyed them. Al-Amin sent agents east to stir opposition to al-Ma'mun. However, a careful watch at the frontier denied these the opportunity. Al-Amin denied al-Ma'mun's request for his family and money and kept them in Baghdad.

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