Demographics of the member states of the Organisation of Islamic Cooperation

This is a list of 57 member states of the Organisation of Islamic Cooperation sorted by their estimated population.
11 countries are not Muslim-majority, but they are members of Organisation of Islamic Cooperation.
Also the list below only includes OIC members, not OIC observers, and does not include many other countries having a significant number of Muslims in their resident population from immigrants and their descendants.
Syria's membership in the Organisation of Islamic Cooperation, of which it is a founding member, was reinstated on March 7, 2025, during the 20th Extraordinary Session of the OIC Council of Foreign Ministers in Jeddah. This followed a suspension that began in August 2012 due to the Syrian civil war. Other member states have also been suspended in the past and later reintegrated into the OIC.