The African Union replaced the Organisation of African Unity and is headquartered in Addis Ababa
Background
The African Union (AU) is a continental body made up of the member states that are the countries of the African continent. It was officially launched in July 2002 in Durban, South Africa, as successor to the Organisation of African Unity (OAU, 1963-1999). In May 1963, 32 Heads of independent African States met in Addis Ababa, Ethiopia, to sign the OAU Charter. On 9 September 1999 the OAU leaders issued the Sirte Declaration calling for an African Union. The Constitutive Act of the African Union lays out the aims of the AU, including greater unity and solidarity between African countries and defending their sovereignty, territorial integrity and independence. The AU Headquarters is in Addis Ababa, and Agenda 2063 is its blueprint for the continent's transformation.
In plain words
OAU Organisation of African Unity — Africa's first post-independence continental body, created by a Charter signed in Addis Ababa.
Agenda 2063 AU strategic framework — The AU's blueprint and master plan for inclusive and sustainable development of Africa.