A one world government is the concept of a political body that would make, interpret and enforce international law. Inherent to the concept of a one world government is the idea that nations would be required to pool or surrender (depending on point of view) sovereignty over some areas. In effect, a world government would add another level of administration above the existing national governments or provide coordination over areas national governments are not capable of adequately addressing as independent polities.

To date, no nation has officially put forward plans for a world government, although some people do see international institutions (such as the International Criminal Court, European Union, United Nations and International Monetary Fund) as the beginning elements of a world government system. An organization comprised of legislators from various nations known as Parliamentarians for Global Action have promoted ideas of democratic global governance, though such promotion has varied in its scope and intensity during the organization's history.

The need for a global government to preserve the peace between nations was discussed in ancient Greek and Roman times, and, in modern times the idea has been recognized since the early 14th century (Dante, for example, discusses it in his book Monarchia, 1329). In 1625, the great Dutch jurist Hugo Grotius wrote De Jure Belli ac Pacis (The Laws of War and Peace), which is commonly taken as the starting-point of modern international law. The idea of a federation gained much momentum during the late 18th century, a period in which the first modern democratic federation, the USA, was established (1788), and in which Immanuel Kant wrote the essay "Perpetual Peace: a philosophical sketch" (1795). In his essay, Kant describes three basic requirements for organizing human affairs to permanently abolish the threat of a future war:

The civil constitution of each state shall be republican
The law of nations shall be founded on a federation of free states.
The rights of people, as citizens of the world, shall be limited to the conditions of universal hospitality (i.e., people would be allowed to visit other countries, but not to stay unless invited).

It should also be noted that to date world governments were not democracies, and over human history there have been many 'world governments' which were empires or dictatorships. Famous examples are Alexander the Great and his empire, the Mongol Empire, and the British Empire, which all encompassed substantial portions of the then known world; in the case of the British, a quarter of the world's surface and approximately a third of the world's population. This is the single closest time that the world has come to a total political unification.

Since then, unsuccessful attempts were made throughout the first half of the 20th century to establish global institutions to resolve international disputes peacefully, or, when these fail, to establish laws in the conduct of wars between nations. The most remarkable ones include the Hague Conferences of 1899 and 1907, which failed to prevent World War I, and the League of Nations (1919-1938), which failed to prevent World War II.

The most relevant model for the incremental establishment of a global federation may be the European Union, which politically unites a large group of widely diverse, some formerly hostile, nations spread over a large geographical area. The EU, which is still evolving, already has many attributes of a federal government, such as open internal borders, a directly elected parliament, a court system and a centralized economic policy.

The EU's lead is being followed by the African Union, the Union of South American Nations, the Central American Parliament, and the Association of Southeast Asian Nations. A multitude of regional associations, aggregating most nations of the world, are at different stages of development towards a growing extent of economic, and sometimes political, integration.