A multinational state or a multinational union is a sovereign entity that comprises two or more nations or states. This contrasts with a nation state, where a single nation accounts for the bulk of the population. Depending on the definition of "nation" (which touches on ethnicity, language, and political identity), a multinational state is usually multicultural or multilingual, and is geographically composed of more than one country, such as the countries of the United Kingdom.
Historical multinational states that have since split into multiple states include the Ottoman Empire, British India, Qing dynasty, Iran (Which contains; Turk, Fars or Persian, Arab, Kurd e.t.c.), Czechoslovakia, the Soviet Union, Yugoslavia and Austria-Hungary (a dual monarchy of two multinational states). Some analysts have described the European Union as a multinational state or a potential one.
Many attempts have been made to define what a multinational state is. One complicating factor is that it is possible for members of a group that could be considered a nation to identify with two different nationalities simultaneously. As Ilan Peleg wrote in Democratizing the Hegemonic State: One can be a Scot and a Brit in the United Kingdom, a Jew and an American in the United States, an Igbo and a Nigerian in Nigeria ... One might find it hard to be a Slovak and a Hungarian, an Arab and an Israeli, a Breton and a Frenchman.
A state may also be a society, and a multiethnic society has people belonging to more than one ethnic group, in contrast to societies that are ethnically homogeneous. By some definitions of "society" and "homogeneous", virtually all contemporary national societies are multiethnic. The scholar David Welsh argued in 1993 that fewer than 20 of the 180 sovereign states then in existence were ethnically and nationally homogeneous, if a homogeneous state was defined as one in which minorities made up less than 5 percent of the population. Sujit Choudhry therefore argues that "[t]he age of the agriculturally homogeneous state, if ever there was one, is over".