O
OAPEC — Organization of Arab Petroleum Exporting Countries
OAS — Organization of American States
OAU — Organization of African Unity
OECD — Organization for Economic Cooperation and Development
OECS — Organization of Eastern Caribbean States
OIC — Organization of the Islamic Conference
ONUMOZ — see UNOMOZ
ONUSAL — United Nations Observer Mission in El Salvador
OPANAL — Organismo para la Proscripcion de las Armas Nucleares en la America Latina y el Caribe; see Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean