Ali ibn Abi Talib, the fourth Rashidun caliph (r. 656–661) and the first Shia Imam, was assassinated during the morning prayer on 28 January 661 CE, equivalent to 19 Ramadan 40 AH.

Ibn Muljim had entered Kufa with the intention of killing Ali, probably in revenge for the Kharijites' defeat in the Battle of Nahrawan in 658.

By most accounts, also involved in the assassination was al-Ash'ath ibn Qays, the influential Kufan tribal leader whose loyalty to Ali is often questioned in the early sources.

[1] Ali ibn Abi Talib, the son-in-law and cousin of the Islamic prophet Muhammad, was subsequently elected caliph by the Medinans and the dissidents present there.

[7][4] By contrast, Ali found limited support among the powerful Quraysh tribe, some of whom aspired to the title of caliph.

[25] The common narrative involves Mu'awiya and his governor of Egypt, Amr ibn al-As, as reported by the Sunni historian al-Tabari (d. 923), among others.

[27] For Laura Veccia Vaglieri (d. 1989), another expert, this narrative is also questionable,[28] but probably generated from a common historical tradition because the variations in the sources are minor in her view.

[24] According to al-Tabari, Ibn Muljim met in Kufa a group of the Taym al-Ribab tribe who were mourning their tribesmen killed at Nahrawan.

[35][36] Before his death, Ali had requested that Ibn Muljim should be executed in retaliation (qisas) if he did not survive,[34] and his wish was fulfilled by his eldest son Hasan.

[28] By other accounts, Ali instead left this decision to Hasan and recommended pardon,[37] asked his men not to bound Ibn Muljim tightly,[38] forbade his tribesmen from shedding Muslim blood beyond a meticulous application of lex talionis to Ibn Muljim, who were to be given good meals and a soft bed in the meantime and not exposed to public ridicule.

[39] Mua'wiya indeed wrote to the Kufan elite after Nahrawan, offering them status and wealth in return for sabotage,[40][41][42] whereas Ali refused to grant them any financial favors as a matter of principle.

[34] Fearing that his body might be exhumed and profaned by his enemies, Ali was then buried secretly,[28] which may also explain the discrepancies in the sources about his burial site.

[32] His grave was identified during the caliphate of the Abbasid Harun al-Rashid (r. 786–809) and the town of Najaf grew around it near Kufa, becoming a major site of pilgrimage for Muslims, especially Shias.

[28] The present shrine was built by the Safavid Shah Safi (r. 1629–1642),[47] near which lies an immense cemetery for Shias who wish to be buried next to their imam.

[48] Among many others, the assassination of Ali has been the subject of paintings by the Iranian artists Yousef Abdinejad,[49] Farhad Sadeghi,[50] and Mansoureh Hosseini,[51] as well as a stage play by Bahram Beyzai.

[56][57] After a failed attempt on his life, a wounded Hasan ceded the rule in August 661 to Mu'awiya, who founded the Umayyad Caliphate.