The Merger Treaty, signed in Brussels on 8 April 1965 and in force since 1 July 1967, first gathered together the organizational structures of the then three European Communities (European Coal and Steel Community, European Economic Community and Euratom). This formal name was Treaty establishing a Single Council and a Single Commission of the European Communities.

It created the European Commission and the Council of the European Communities to be the governing bodies for all three institutions, and it also had them share a single budget. This treaty is regarded by some as the real beginning of the modern European Union. The term European Communities or EC also came into use from this time onward.

It was abrogated by Amsterdam Treaty signed in 1997 which comprehended its mantle.

Timeline of the Treaties and EU Constitution

European Union treaties

Tractat de fusió de les Comunitats Europees | Slučovací smlouva | Vertrag zur Einsetzung eines gemeinsamen Rates und einer gemeinsamen Kommission der Europäischen Gemeinschaften | Tratado de Bruselas | Traité de fusion | Egyesítő szerződés | Fusieverdrag | ブリュッセル条約 | Traktat fuzyjny | Tratatul de fuziune | Zmluvy o Európskych spoločenstvách