The Czechoslovak Declaration of Independence or the Washington Declaration was drafted in Washington, D.C., and published by Czechoslovakia's Paris-based Provisional Government on 18 October 1918. The creation of the document, officially the Declaration of Independence of the Czechoslovak Nation by Its Provisional Government, was prompted by the imminent collapse of the Habsburg Austro-Hungarian Empire, of which the Czech and Slovak lands had been part for almost 400 years, following the First World War.

The First Czechoslovak Republic, often colloquially referred to as the First Republic, was the first Czechoslovak state that existed from 1918 to 1938, a union of ethnic Czechs and Slovaks. The country was commonly called Czechoslovakia, a compound of Czech and Slovak; which gradually became the most widely used name for its successor states. It was composed of former territories of Austria-Hungary, inheriting different systems of administration from the formerly Austrian and Hungarian territories.