The United States of Europe is a name often given to one possible future development of the European Union, where the union assumes more powers from its member countries and starts to act like a confederation or federation, more like the United States of America. This name is used both by those who embrace such a development, and by those who oppose it. Views on this topic are different across the traditional left-right political scale and between different parts of Europe. Some countries have good experience of being neutral and independent and joined the union only reluctantly (e.g. Sweden, where the result of the referendum on membership was only 51-49 in favour), while others joined the union with more enthusiasm (e.g. Spain).

The phrase "United States of Europe" was used by Winston Churchill in a famous speech in 1948 at the University of Zürich, which is frequently credited with beginning the process that led to the formation of the European Union. See History of the European Union

It was also used several times by Victor Hugo (États-Unis d’Europe), including during a speech at the French National Assembly, on March 1, 1871.

In June 2003, European integration went one step further by the submission of a new 220-page European constitutional text drafted by the Convention on the Future of Europe under leadership of former French president Valery Giscard d'Estaing, to the 25 EU heads of government who expect to be ruled by it soon. The constitution is supposed to replace all of the current EU treaties.

The draft, designed to make the EU more effective, but also more democratic, calls for the election of an EU president who may serve for up to five years and for a foreign minister.