Classical architecture typically refers to architecture consciously derived from the principles of Greek and Roman architecture of classical antiquity, or more specifically, from De architectura (c. 10 AD) by the Roman architect Vitruvius. Variations of classical architecture have arguably existed since the Carolingian Renaissance, and became especially prominent during the Italian Renaissance and the later period known as neoclassical architecture or Classical revival. While classical styles of architecture can vary, they generally share a common "vocabulary" of decorative and structural elements. Across much of the Western world, classical architectural styles have dominated the history of architecture from the Renaissance until World War II. Classical architecture continues to influence contemporary architects.

The term classical architecture can also refer to any architectural tradition that has evolved to a highly refined form, such as classical Chinese or Mayan architecture. It may also describe architecture that adheres to classical aesthetic philosophy. The term might be used differently from "traditional" or "vernacular architecture", it can share underlying axioms with it.

For contemporary buildings following authentic classical principles, the term New Classical architecture is often used.

Classical architecture is derived from the architecture of ancient Greece and ancient Rome. After the collapse of the western part of the Roman empire, the architectural traditions of the Roman Empire ceased to be practised in large parts of western Europe. In the Byzantine Empire, however, ancient ways of building methods survived, though they gradually developed into a distinct Byzantine style. The first conscious attempts to bring back the architectural language of classical antiquity into Western Europe emerged during the Carolingian Renaissance of the late 8th and 9th centuries. The gatehouse of Lorsch Abbey (c. 800) in present-day Germany features alternating attached columns and archesl an almost direct paraphrase of e.g., that of the Colosseum in Rome.

While Byzantine, Romanesque, and even to some aspects of Gothic architecture (with which classical architecture is often posed) incorporate classical elements and details, they generally do not reflect a systematic effort to revive or emulate the architectural principles of antiquity. For instance, they typically do not adhere the idea of a systematic order of proportions for columns. As such, these styles are not considered classical architecture in the strict sense.

During the Italian Renaissance and with the demise of Gothic style, major efforts were made by architects such as Leon Battista Alberti, Sebastiano Serlio and Giacomo Barozzi da Vignola to revive the language of architecture of first and foremost ancient Rome. This was done in part through the study of the ancient Roman architectural treatise De architectura by Vitruvius, and to some extent by studying the actual remains of ancient Roman buildings in Italy. Nonetheless, the classical architecture of the Renaissance from the outset represents a highly specific interpretation of the classical ideas. In a building like the Ospedale degli Innocenti in Florence by Filippo Brunelleschi, one of the earliest Renaissance buildings (built 1419–1445), the treatment of the columns for example has no direct antecedent in ancient Roman architecture. During this time period, the study of ancient architecture developed into the architectural theory of classical architecture; somewhat over-simplified, that classical architecture in its variety of forms ever since have been interpretations and elaborations of the architectural rules set down during antiquity.

Most of the styles originating in post-Renaissance Europe can be described as classical architecture. This broad use of the term is employed by Sir John Summerson in The Classical Language of Architecture. The elements of classical architecture have been applied in radically different architectural contexts than those for which they were developed, however. For example, Baroque or Rococo architecture are styles which, although classical at root, display an architectural language much in their own right. During these periods, architectural theory still referred to classical ideas but rather less sincerely than during the Renaissance.

The Palladian architecture developed from the style of the Venetian architect Andrea Palladio (1508–1580) had a great influence long after his death, above all in Britain, where it was adopted for many of the grander buildings of the Georgian architecture of the 18th and early 19th century.