In architecture, Rationalism is an architectural current which mostly developed from Italy in the 1920s and 1930s. Vitruvius had claimed in his work De architectura that architecture is a science that can be comprehended rationally. The formulation was taken up and further developed in the architectural treatises of the Renaissance. Eighteenth-century progressive art theory opposed the Baroque use of illusionism with the classic beauty of truth and reason.

The International Style or internationalism is a major architectural style that was developed in the 1920s and 1930s and was closely related to modernism and modernist architecture. It was first defined by Museum of Modern Art curators Henry-Russell Hitchcock and Philip Johnson in 1932, based on works of architecture from the 1920s. The terms rationalist architecture and modern movement are often used interchangeably with International Style, although the former is mostly used in the English-speaking world to specifically refer to the Italian rationalism, or even the International Style that developed in Europe as a whole.