The Organisation of Islamic Cooperation (OIC; Arabic: منظمة التعاون الاسلامي‎; French: Organisation de la Coopération Islamique (OCI)) is an international organisation consisting of 57 member states. The organisation attempts to be the collective voice of the Muslim world (Ummah) and attempts to safeguard the interests and ensure the progress and well-being of Muslims.

The OIC has a permanent delegation to the United Nations, and is the largest international organisation outside of the United Nations. The official languages of the OIC are Arabic, English, and French. It changed its name on 28 June 2011 from the Organisation of the Islamic Conference (Arabic: منظمة المؤتمر الإسلامي‎; French: Organisation de la Conférence Islamique) to its current name.

Since the 19th century, some Muslims had aspired to ummah to serve their common political, economic, and social interests. The collapse of the Ottoman Empire and the Caliphate after World War I left a vacuum for a pan-Islamic institution. Losing the Arab-Israeli War provided the incentive needed in 1967. Leaders of Muslim nations met in Rabat to establish the OIC on September 25, 1969.