Iraq's Muslims follow two distinct traditions, Shia and Sunni Islam. Iraq is home to many religious cities important for both Shia and Sunni Muslims. Baghdad was a hub of Islamic learning and scholarship for centuries and served as the capital of the Abassids. The city of Karbala has substantial prominence in Shia Islam as a result of the Battle of Karbala, fought on the site of the modern city on October 10, 680. Similarly, Najaf is renowned as the site of the tomb of Alī ibn Abī Tālib (also known as "Imām Alī"), whom the Shia consider to be the righteous caliph and first imām. The city is now a great center of pilgrimage from throughout the Shi'a Islamic world and it is estimated that only Mecca and Medina receive more Muslim pilgrims. The city of Kufa was home to the famed scholar Abu Hanifah, whose school of thought is followed by a sizable number of Sunni Muslims across the globe. Likewise, Samarra is also home to the al-Askari Mosque, containing the mausoleums of the Ali al-Hadi and Hasan al-Askari, the tenth and eleventh Shia Imams respectively, as well as the shrine of Muhammad al-Mahdi, known as the "Hidden Imam", who is the twelfth and final Imam of the Shia of the Ja'farī Madhhab. This has made it an important pilgrimage centre for Ja'farī Shia Muslims. In addition, some female relatives of Muhammad are buried in Samarra, making the city one of the most significant sites of worship for Shia and a venerated location for Sunni Muslims.
Smaller sects of Islam exist in the country, such as the small Shaykhist community concentrated in Basra and Karbala.
The Muslim population of Iraq is approximately 60-70 percent Arab Shi'a, 20-30 percent Arab Sunni and 10 percent Kurdish. Iraqi Kurds are mostly Sunni, with about 10% being Shi'a Faili Kurds. Most Kurds are located in the northern areas of the country, with most following the Shafi school of Islamic law. With some being members of either the Qadiri or the NaqshbandiSufitariqah.