In architecture, functionalism is the principle that buildings should be designed based solely on their purpose and function. An international functionalist architecture movement emerged in the wake of World War I, as part of the wave of Modernism. Its ideas were largely inspired by a desire to build a new and better world for the people, as broadly and strongly expressed by the social and political movements of Europe after the extremely devastating world war. In this respect, functionalist architecture is often linked with the ideas of socialism and modern humanism.

A new slight addition to this new wave of functionalism was that not only should buildings and houses be designed around the purpose of functionality, architecture should also be used as a means to physically create a better world and a better life for people in the broadest sense. This new functionalist architecture had the strongest impact in Czechoslovakia, Germany, Poland, the USSR and the Netherlands, and from the 1930s also in Scandinavia and Finland.

This principle is a matter of confusion and controversy within the profession, particularly in regard to modern architecture, as it is less self-evident than it first appears.