Abū Mūsā Muḥammad bin Hārūn al-Amīn (Arabic: أبو موسى محمد بن هارون الأمين; April 787 – 24/25 September 813), better known by his laqab of al-Amin (Arabic: الأمين, romanized: al-Amīn), was the sixth Abbasid caliph from 809 to 813.

Al-Amin succeeded his father, Harun al-Rashid, in 809 and ruled until he was deposed and killed in 813, during the civil war by his half-brother, al-Ma'mun.

However, Abdallah's mother was a Persian slave concubine, and his pure Abbasid lineage gave Muhammad seniority over his half-brother.

[2][3] These arrangements were confirmed and publicly proclaimed in 802, when Harun and the most powerful officials of the Abbasid government made the pilgrimage to Mecca.

[6] The stipulations of the agreement, which were recorded in detail by the historian al-Tabari, accorded al-Mamun's Khurasani viceroyalty extensive autonomy.

[7] Harun's third heir, al-Mu'tamin, received responsibility over the frontier areas with the Byzantine Empire in Upper Mesopotamia and Syria.

[2][3] These complex arrangements, sealed with mutual judicial and religious oaths, clearly demonstrate that Harun was conscious of their precariousness, in view of the profound differences between al-Amin and al-Ma'mun, both in character and in interests.

[1] Very quickly, this latent rivalry had important repercussions: almost immediately after the court returned to Baghdad in January 803, the Abbasid elites were shaken by the abrupt fall of the Barmakid family from power.

[2][8][9] Indeed, the years after the fall of the Barmakids saw an increasing centralization of the administration and the concomitant rise of the influence of the abnāʾ, many of whom were now dispatched to take up positions as provincial governors and bring these provinces under closer control from Baghdad.

Al-Ma'mun was sent ahead with part of the army to Marv, while Harun stayed at Tus, where he died on 24 March 809.

The majority of army commanders on the Khorasan expedition decided to obey new caliph's order to return to Baghdad.

Under the influence of their respective ministers, al-Amin and al-Ma'mun took steps that further polarized the political climate and made the breach irreparable.

Al-Ma'mun replied by declaring himself imam, a religious title which shied of directly challenging the Caliph but nevertheless implied independent authority, as well as hearkening back to the early days of the Hashimiyya movement which had carried the Abbasids to power.

[13][14][15] Despite the reservations of some of his senior ministers and governors, two months later, in January 811, al-Amin formally began the civil war when he appointed Ali ibn Isa governor of Khurasan, placed him at the head of an unusually large army of 40,000 men, drawn from the abnaʾ, and sent him to depose al-Ma'mun.

In Mecca, Dawud ibn Isa reminded worshippers that al-Amin had destroyed Harun ar Rashid's succession pledges and led them in swearing allegiance to al-Mamun.

[17] However, al-Amin died before the consummation of his marriage to Lubanah; her attested poetry includes a lament for his death: 'Oh hero lying dead in the open, betrayed by his commanders and guards.

Described as charming with fair skin, she was praised for her musical talent, particularly her skill in playing instruments, and was known for her exceptional ability as a songwriter and singer.

Abdullah, who spent an extended period in the courts of subsequent caliphs, was the sole individual to continue the lineage of al-Amin.

In an effort to dissuade her son from Kauthar, al-Amin's mother insisted that his female slaves dress in men's attire to encourage him to engage in sexual relationships with them.

There were several vicious battles, such as at al-Amin's palace of Qasr Halih, at Darb al- Hijarah and the al-Shammasiyyah Gate.

Tahir reluctantly agreed on the condition al-Amin turn over his sceptre, seal and other symbols of office.

However, Tahir noticed the boat, and al-Amin was thrown into the water, swam to shore, was captured and then brought to a room, where he was executed.

197–202) quotes Tahir's letter to al-Ma'mun informing him of al-Amin's capture and execution and the state of peace resulting in Baghdad.