Founded in 1969 consisting of 57 member states, the organisation states that it is "the collective voice of the Muslim world". It was set up as result of the collapse of the Ottoman Empire and the Caliphate after World War I left a vacuum for a pan-Islamic institution. Losing the Six-Day War in 1967 provided the incentive needed where leaders of Muslim nations met in Rabat to establish the OIC on 25 September 1969.
57 states, you say?
“Suleiman and the Ottomans” Reunion Tour 2016