The United States of Europe, the European state, the European superstate, the European federation and Federal Europe are names used to refer to several similar hypothetical scenarios of the unification of Europe as a single sovereign federation of states (hence superstate), similar to the United States of America, both as projected by writers of speculative fiction and science fiction and by political scientists, politicians, geographers, historians and futurologists. At present, while the European Union (EU) is not officially a federation, various academic observers regard it as having the characteristics of a federal system.
Specifically, the term "United States of Europe" – as a direct comparison with the United States of America – would imply that all the European states would acquire a status similar to that of a U.S. state, becoming constituent parts of a European federation acting as one country.
Traditionally, the term "European Superstate", particularly within the United Kingdom, is used as a criticism of further integration into the EU with the term implying a forced loss of national sovereignty, although the term has occasionally been used positively in the British press.
Various versions of the concept have developed over the centuries, many of which are mutually incompatible (inclusion or exclusion of the United Kingdom, secular or religious union, etc.). Such proposals include those from Bohemian King George of Podebrady in 1464; Duc de Sully of France in the seventeenth century; and the plan of William Penn, the Quaker founder of Pennsylvania, for the establishment of a "European Dyet, Parliament or Estates". George Washington also allegedly voiced support for a "United States of Europe", although the authenticity of this statement has been questioned.
Felix Markham notes how, during a conversation on St. Helena, Napoleon Bonaparte remarked: "Europe thus divided into nationalities freely formed and free internally, peace between States would have become easier: the United States of Europe would become a possibility". "United States of Europe" was also the name of the concept presented by Wojciech Jastrzębowski in About eternal peace between the nations, published 31 May 1831. The project consisted of 77 articles. The envisioned United States of Europe was to be an international organisation rather than a superstate. Giuseppe Mazzini was an early advocate of a "United States of Europe" and regarded European unification as a logical continuation of the unification of Italy. Mazzini created the Young Europe movement.
The term "United States of Europe" (French: États-Unis d'Europe) was used by Victor Hugo, including during a speech at the International Peace Congress held in Paris in 1849. Hugo favoured the creation of "a supreme, sovereign senate, which will be to Europe what parliament is to England" and said: "A day will come when all nations on our continent will form a European brotherhood ... A day will come when we shall see ... the United States of America and the United States of Europe face to face, reaching out for each other across the seas". Hugo planted a tree in the grounds of his residence on the Island of Guernsey and was noted in saying that when this tree matured the United States of Europe would have come into being. This tree to this day is still growing in the gardens of Maison de Hauteville, St. Peter Port, Guernsey, Victor Hugo's residence during his exile from France.
The Italian philosopher Carlo Cattaneo wrote: "The ocean is rough and whirling, and the currents go to two possible endings: the autocrat, or the United States of Europe". In 1867, Giuseppe Garibaldi and John Stuart Mill joined Victor Hugo at a congress of the League for Peace and Freedom in Geneva. Here the anarchist Mikhail Bakunin stated: "That in order to achieve the triumph of liberty, justice and peace in the international relations of Europe, and to render civil war impossible among the various peoples which make up the European family, only a single course lies open: to constitute the United States of Europe". The French National Assembly also called for a United States of Europe on 1 March 1871.