Functionalism, in architecture, is the principle that architects should design a building based on the purpose of that building. This statement is less self-evident than it first appears, and is a matter of confusion and controversy within the profession, particularly in regard to modern architecture.

The place of functionalism in building can be traced back to the Vitruvian triad, where 'utilitas' (variously translated as 'commodity', 'convenience', or 'utility') stands alongside 'venustas' (beauty) and 'firmitas' (firmness) as one of three classic goals of architecture. Functionalist views were typical of some gothic revival architects, in particular Augustus Welby Pugin wrote that "there should be no features about a building which are not necessary for convenience, construction, or propriety" and "all ornament should consist of enrichment of the essential construction of the building".

The debate about functionalism and aesthetics is often framed as a mutually exclusive choice, when in fact there are architects, like Will Bruder, James Polshek and Ken Yeang, who attempt to satisfy all three Vitruvian goals.^{[citation needed]}