Muhammad Baqir al-Sadr in the context of Muqtada al-Sadr

Shia Islamism is the implementation of Shia Islam in politics. Most study and reporting on Islamism has been focused on Sunni Islamist movements. Shia Islamism, a previously very small ideology, gained in popularity after the Iranian Revolution (1978–1979) led by Ruhollah Khomeini, whose Shia Islamist policies became known as Khomeinism. Khomeini's form of Islamism was unique not only for being a powerful political movement which successfully came to power, but for having completely swept away the old regime, created a new one with a new constitution, new institutions and a new concept of governance (the velayat-e-faqih). A historical event, it changed militant Islam from a topic of limited impact and interest, to one that few inside or outside the Muslim world were unaware. However, there are also Shia Islamist movements outside of Khomeinism, such as the Islamic Dawa Party of Muhammad Baqir al-Sadr and the Sadrist Movement of Muqtada al-Sadr.

Though a minority of the world Muslim community, Twelver Shias form the majority of the population in the countries of Iran, Iraq, and Azerbaijan, and substantial minorities in Afghanistan, Bahrain, India, Lebanon, Kuwait, Pakistan, Qatar, Syria, Saudi Arabia and the United Arab Emirates.