The Battle of Nahrawan (Arabic: مَعْرَكَة النَّهْرَوَان, romanized: Ma'rakat an-Nahrawān) was fought between the army of Caliph Ali and the rebel group Kharijites in July 658 CE (Safar 38 AH).

They separated from him following the Battle of Siffin when Ali agreed to settle the dispute with Mu'awiya, governor of Syria, through negotiations, a move labeled by the group as against the Qur'an.

After failed attempts to regain their loyalty and because of their rebellious and murderous activities, Ali confronted the Kharijites near their headquarters by the Nahrawan Canal, near modern-day Baghdad.

Ali ibn Abi Talib, the son-in-law and cousin of Muhammad, was subsequently elected Caliph by the Medinese people.

An arbitration committee was setup with representatives from Ali's and Mu'awiya's sides with a mandate to settle the dispute in the spirit of the Qur'an.

A group of his soldiers criticized the arbitration and accused Ali of blasphemy for leaving the matter to the discretion of two men and not acting according to the Book of God.

[3] According to some accounts, they returned on the condition that the war against Mu'awiya be resumed after six months and Ali acknowledge his mistake, which he did on general and ambiguous terms.

In order to avoid being detected, they moved out in small groups and went to a place by the Nahrawan Canal on the east bank of the Tigris.

[19] After further exchanges, the Kharijite leaders instructed their followers not to engage in further discussion and instead prepare for martyrdom and to meet their Lord in paradise.

Both sides arranged in battle order and Ali announced an amnesty for any Kharijite who would join him or return to Kufa and that only murderers would be punished.

[20] About 1,200 Kharijites accepted his offer, some joining Ali's army, others returning to Kufa or leaving the battlefield for refuge in the mountains; Ibn Wahb was consequently left with 2,800 fighters.

Ali agreed and moved to Nukhayla, a mustering ground outside Kufa, and permitted his soldiers to rest and occasionally visit their homes.

During the Second Fitna they controlled large parts of Arabia and Persia, but were later subdued by the Umayyad governor of Iraq, al-Hajjaj ibn Yusuf.