Shia Islam in Iraq

Shia Islam in Iraq (Arabic: الشيعة في العراق) has a history going back to the times of Ali ibn Abi Talib who moved the capital of the Rashidun Caliphate from Medina to Kufa, two decades after the death of Muhammad. Iraqi Shias constitute the chief component of Iraqi society and the term is used as a socio-political and religious identifier. Their historical stronghold has been Lower Mesopotamia, historically known as Babylonia.

Those identifying as Shia vary between religious, moderately religious and secular. Since Iraq is a predominantly tribal society, one's sectarian affiliation is often dependent on one's tribe regardless of personal religious convictions or lack thereof. Since 2005, due to Muhasasah, an informally adopted political system of sect-based power sharing, sectarian stratification has occurred for political reasons. The vast majority of Iraqi Shias are ethnically Arab.

Shia Muslims are generally considered to constitute the majority of the Iraqi population with varying estimates over their percentages, such as a lower estimate reporting it to be between 55% and 60%, and a higher estimate ranging between 64% and 69% of the population of Iraq. Iraq is the location of the holy cities of Najaf and Karbala, in addition to Kadhimiya and Samarra, pilgrimage sites for millions of Shia Muslims. Modern Iraqi Shias follow the Twelver sect. Historically, there were followers of Isma'ilism among Musha'sha' Arabs, Zaydism among Kurds, and Ibrahimiyya among Turkmen, which all declined. Since 2010, the number of people identifying as atheists has increased, especially among the youth.

Najaf is the site of Ali's tomb, and Karbala is the site of the tomb of Muhammad's grandson, third Shia Imam Husayn ibn Ali. Najaf is also a center of Shia learning and seminaries. Two other holy sites for Twelver Shia in Iraq are the Al-Kadhimiya Mosque in Baghdad, which contains the tombs of the seventh and ninth Shia Imams (Mūsā al-Kādhim and Muhammad al-Jawad) and the Al-Askari Mosque in Samarra, which contains the tombs of the tenth and eleventh Shia Imams (Ali al-Hadi and Hasan al-‘Askarī).

Iraq is known as the center of Shia Islam, with Najaf being the hub of Shia scholarship. After the U.S.-led invasion in 2003, widespread sectarian violence erupted between Shias and Sunnis in Iraq, which led to war in 2006–2008 and 2013–2017, with the latter one involving the Islamic State.