The Organisation of Eastern Caribbean States (OECS) is an International, Inter-governmental Organisation dedicated to regional integration in the Eastern Caribbean. It consists of 11 countries, seven of which are Protocol Member States: Antigua and Barbuda, Commonwealth of Dominica, Grenada, Montserrat, Saint Kitts and Nevis, Saint Lucia, and Saint Vincent and The Grenadines. The remaining four, the British Virgin Islands, Anguilla, Martinique, and Guadeloupe, are Associate Member States.

The OECS came into being on June 18, 1981, with the signing of the Treaty of Basseterre. This Treaty was replaced in 2010 with the Revised Treaty of Basseterre, creating a single financial and economic space where goods, people, and capital move freely within Protocol Member States.