The Economic Community of West African States, also known as ECOWAS, is a regional economic union of fifteen countries located in West Africa. Collectively, these countries comprise an area of 5,114,162 km2 (1,974,589 sq mi), and in 2015 had an estimated population of over 349 million.
The union was established on 28 May 1975, with the signing of the Treaty of Lagos, with its stated mission to promote economic integration across the region. A revised version of the treaty was agreed and signed on 24 July 1993 in Cotonou. Considered one of the pillar regional blocs of the continent-wide African Economic Community (AEC), the states goal of ECOWAS is to achieved "collective self-sufficiency" for its member states by creating a single large trade bloc by building a full economic and trading union.
ECOWAS also serves as a peacekeeping force in the region, with member states occasionally sending joint military forces to intervene in the bloc's member countries at times of political instability and unrest. In recent years these included interventions in Ivory Coast in 2003, Liberia in 2003, Guinea-Bissau in 2012, Mali in 2013, and Gambia in 2017.ECOWAS includes two sub-regional blocs:

The West African Economic and Monetary Union (also known by its French-language acronym UEMOA) is an organization of eight, mainly French-speaking, states within the ECOWAS which share a customs union and currency union. Established in 1994 and intended to counterbalance the dominance of English-speaking economies in the bloc (such as Nigeria and Ghana), members of UEMOA are mostly former territories of French West Africa. The currency they all use is the CFA franc, which is pegged to the euro.
The West African Monetary Zone (WAMZ), established in 2000, comprises six mainly English-speaking countries within ECOWAS which plan to work towards adopting their own common currency, the eco.ECOWAS operates in three co-official languages—French, English, and Portuguese, and consists of two institutions to implement policies: the ECOWAS Commission and the ECOWAS Bank for Investment and Development (EBID), formerly known as the Fund for Cooperation until it was renamed in 2001. A few members of the organization have come and gone over the years. In 1976 Cape Verde joined ECOWAS, and in December 2000 Mauritania withdrew, having announced its intention to do so in December 1999.
In 2011, ECOWAS adopted its development blueprint for the next decade, Vision 2020, and, to accompany it, a Policy on Science and Technology (ECOPOST).