Member States
The AU is made up of 55 Member States which represent all the countries on the African continent. AU Member States are divided into five geographic regions. which were defined by the OAU in 1976 (CM/Res.464QCXVI).
The following list shows all members states grouped by region, in alphabetical order, and their date of joining the AU or its predecessor the OAU.
Central Africa
| Member State | Abbreviation | Date of joining the OAU or AU |
| Republic of Burundi | Burundi | 25 May 1963 |
| Republic of Cameroon | Cameroon | 25 May 1963 |
| Central African Republic | Central African Republic | 25 May 1963 |
| Republic of Chad | Chad | 25 May 1963 |
| Republic of the Congo | Congo Republic | 25 May 1963 |
| Democratic Republic of Congo | DR Congo | 25 May 1963 |
| Republic of Equatorial Guinea | Equatorial Guinea | 12 October 1968 |
| Gabonese Republic | Gabon | 25 May 1963 |
| Democratic Republic of São Tomé and Príncipe | São Tomé and Príncipe | 18 July 1975 |
Eastern Africa
| Member State | Abbreviation | Date of joining the OAU or AU |
| Union of the Comoros | Comoros | 18 July 1975 |
| Republic of Djibouti | Djibouti | 27 June 1977 |
| State of Eritrea | Eritrea | 24 May 1993 |
| Federal Democratic Republic of Ethiopia | Ethiopia | 25 May 1963 |
| Republic of Kenya | Kenya | 25 May 1963 |
| Republic of Madagascar | Madagascar | 25 May 1963 |
| Republic of Mauritius | Mauritius | August 1968 |
| Republic of Rwanda | Rwanda | 25 May 1963 |
| Republic of Seychelles | Seychelles | 29 June 1976 |
| Federal Republic of Somalia | Somalia | 25 May 1963 |
| Republic of South Sudan | South Sudan | 27 July 2011 |
| Republic of the Sudan | Sudan | 25 May 1963 |
| United Republic of Tanzania | Tanzania | 25 May 1963 |
| Republic of Uganda | Uganda | 25 May 1963 |
Northern Africa
| Member State | Abbreviation | Date of joining the OAU or AU |
| People’s Democratic Republic of Algeria | Algeria | 25 May 1963 |
| Arab Republic of Egypt | Egypt | 25 May 1963 |
| Libya | Libya | 25 May 1963 |
| Islamic Republic of Mauritania | Mauritania | 25 May 1963 |
| Kingdom of Morocco | Morocco | 1963/31 January 2017 |
| Sahrawi Arab Democratic Republic | Sahrawi Republic | 22 February 1982 |
| Republic of Tunisia | Tunisia | 25 May 1963 |
Southern Africa
| Member State | Abbreviation | Date of joining the OAU or AU |
| Republic of Angola | Angola | 11 February 1975 |
| Republic of Botswana | Botswana | 31 October 1966 |
| Kingdom of Eswatini | Eswatini | 24 September 1968 |
| Kingdom of Lesotho | Lesotho | 31 October 1966 |
| Republic of Malawi | Malawi | 13 July 1964 |
| Republic of Mozambique | Mozambique | 18 July 1975 |
| Republic of Namibia | Namibia | June 1990 |
| Republic of South Africa | South Africa | 6 June 1994 |
| Republic of Zambia | Zambia | 16 December 1964 |
| Republic of Zimbabwe | Zimbabwe | 18 June 1980 |
Western Africa
| Member State | Abbreviation | Date of joining the OAU or AU |
| Republic of Benin | Benin | 25 May 1963 |
| Burkina Faso | Burkina Faso | 25 May 1963 |
| Republic of Cabo Verde | Cabo Verde | 18 July 1975 |
| Republic of Côte d’Ivoire | Côte d’Ivoire | 25 May 1963 |
| Republic of the Gambia | Gambia | 9 March 1965 |
| Republic of Ghana | Ghana | 25 May 1963 |
| Republic of Guinea | Guinea | 25 May 1963 |
| Republic of Guinea-Bissau | Guinea-Bissau | 19 November 1973 |
| Republic of Liberia | Liberia | 25 May 1963 |
| Republic of Mali | Mali | 25 May 1963 |
| Republic of Niger | Niger | 25 May 1963 |
| Federal Republic of Nigeria | Nigeria | 25 May 1963 |
| Republic of Senegal | Senegal | 25 May 1963 |
| Republic of Sierra Leone | Sierra Leone | 25 May 1963 |
| Togolese Republic | Togo | 25 May 1963 |