The European Federalist Movement (Movimento Federalista Europeo, MFE) was founded in Milan in 1943 by a group of activists led by Altiero Spinelli.

The principles which inspired its foundation are contained in the Ventotene Manifesto, drawn up in 1941 by Spinelli himself, Eugenio Colorni, Ursula Hirschmann and Ernesto Rossi, and circulated by the in May 1943 circulated L'Unità europea periodical.

[2][1] Vayssière notes that the manifesto is widely seen as the birth of European federalism.

Spinelli (1907–86), a former Communist, became a leader of the federalist movement due to his primary authorship of the Manifesto and his postwar advocacy.

According to the federalists, the new line between progressive and reactionary forces was the one that existed between those for whom the key task is to create a federal European state, and those who consciously or de facto acted to maintain a diversity of sovereign nation-states.