Ali ibn Abi Talib, the fourth Rashidun Caliph and first shia Imam, was assassinated on 26 January 661 by a Kharijite named Abd al-Rahman ibn 'Amr ibn Muljam al-Muradi at the Great Mosque of Kufa, located in present-day Iraq. Ali died from his wounds two days after Abd al-Rahman struck him over his head with a poison-coated sword. He was 62 or 63 years of age at the time of his death on 21 (or 19) Ramadan 40 AH, equivalent to 28 January 661 CE.Ali was elected as the caliph after the assassination of Uthman in 656 but faced opposition from some factions including Mu'awiya, the incumbent governor of present-day Syria. As a result, the first Muslim civil war, known as the First Fitna, followed the assassination of Uthman, continued throughout the four-year reign of Ali, and ended with the overthrow of the Rashidun Caliphate and the establishment of the Umayyad dynasty by Mu'awiya. Notably, when Ali agreed to arbitration with Mu'awiya after the Battle of Siffin in 657, a faction of his army revolted against him. These later became known as the Kharijites (Khawarij, lit.'those who secede'). They soon began to terrorize the civilian population and were crushed by Ali's forces in the Battle of Nahrawan in July 658.Ibn Muljam met in Mecca with two other Kharijites, namely, al-Burak ibn Abd Allah and Amr ibn Bakr al-Tamimi, and concluded that Ali, Mu'awia, and his governor of Egypt, Amr ibn al-As, were to blame for the civil war. They decided to kill the three in order to resolve the "deplorable situation" of Muslims and also avenge their fallen companions at Nahrawan. With the intention of killing Ali, Ibn Muljam headed to Kufa, where he fell in love with a woman whose brother and father were also killed at Nahrawan. She agreed to marry Ibn Muljam on the condition that he would kill Ali and also assisted him in the enterprise. After stabbing Ali at the Great Mosque of Kufa, Ibn Muljam was executed as punishment by Ali's eldest son, Hasan.

The Rashidun Caliphate (Arabic: اَلْخِلَافَةُ ٱلرَّاشِدَةُ, romanized: al-Khilāfah ar-Rāšidah) was the first caliphate to succeed the Islamic prophet Muhammad. It was ruled by the first four successive caliphs (successors) of Muhammad after his death in 632 CE (AH 11). These caliphs are collectively known in Sunni Islam as the Rashidun, or "Rightly Guided" caliphs (اَلْخُلَفَاءُ ٱلرَّاشِدُونَ, al-Khulafāʾ ar-Rāšidūn). This term is not used in Shia Islam, as Shia Muslims do not consider the rule of the first three caliphs legitimate.The Rashidun Caliphate is characterized by a twenty-five-year period of rapid military expansion followed by a five-year period of internal strife. The Rashidun Army numbered more than 100,000 men at its peak. By the 650s, in addition to the Arabian Peninsula, the caliphate had subjugated the Levant to the Transcaucasus in the north; North Africa from Egypt to present-day Tunisia in the west; and the Iranian Plateau to parts of Central Asia and South Asia in the east. The four Rashidun caliphs were chosen by a small electoral body consisting of prominent members of the Quraysh tribal confederation called shūrā (Arabic: شُـوْرَى, lit. 'consultation').The caliphate arose out of the death of Muhammad in 632 CE and the subsequent debate over the succession to his leadership. Abu Bakr, a close companion of Muhammad from the Banu Taym clan, was elected the first Rashidun leader and began the conquest of the Arabian Peninsula. He ruled from 632 to his death in 634. Abu Bakr was succeeded by Umar, his appointed successor from the Banu Adi clan, who continued the conquest of Persia, eventually leading to the fall of the Sasanian Empire in 651. Umar was assassinated in 644 by a Persian slave and was succeeded by Uthman, a member of the Banu Umayya clan, who was elected by a six-person committee arranged by Umar. Under Uthman, the conquest of Armenia, Fars and Khorasan began.Uthman was assassinated by Egyptian rebels in 656 and succeeded by Ali, a member of Muhammad's Banu Hashim clan, who presided over the civil war known as the First Fitna (656–661). The war was primarily between those who believed Uthman was unlawfully killed, supporting his cousin and governor of the Levant Muawiyah, and those who believed his killing was deserved, supporting the caliph Ali. The civil war permanently consolidated the divide between Sunni and Shia Muslims, with Shia Muslims believing Ali to be the first rightful caliph and Imam after Muhammad, favouring his bloodline connection to Muhammad. Additionally, a third faction in the war believed both Ali and Muawiyah should be deposed and a new caliph elected by shura; this faction supported the governor of Egypt Amr ibn al-As. The war led to the end of the Rashidun Caliphate and the establishment of the Umayyad Caliphate in 661 under Muawiyah.