Nigeria is a member of ECOWAS, the OAU (now known as the African Union), and the UNO (now known as the United Nations).
ECOWAS (Economic Community of West African States) is a regional organization consisting of 15 West African countries, with a mandate to promote economic integration and development in the region. Nigeria is one of the founding members of ECOWAS, and it plays a significant role in the organization's affairs.
The OAU (Organization of African Unity) was established in 1963 to promote unity and solidarity among African states and to work towards the decolonization of the continent. The OAU has since been replaced by the African Union, which is a similar organization with a broader mandate. Nigeria was one of the founding members of the OAU and continues to be an active member of the African Union.
The UNO (United Nations Organization) is an international organization established in 1945 to promote international cooperation and maintain international peace and security. Nigeria is a member of the UN and has been actively involved in its affairs since gaining independence in 1960.
Nigeria is not a member of NATO, the Commonwealth of Nations, or the OAS (Organization of American States). It is, however, a member of OPEC (Organization of Petroleum Exporting Countries), which is a group of 13 oil-producing countries that coordinate their petroleum policies to stabilize oil markets and ensure a regular supply of petroleum to consumers.