The Renaissance (UK: rin-AY-sənss, US: (listen) REN-ə-sahnss) is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass ideas and achievements of classical antiquity. It occurred after the Crisis of the Late Middle Ages and was associated with great social change. In addition to the standard periodization, proponents of a "long Renaissance" may put its beginning in the 14th century and its end in the 17th century.

The traditional view focuses more on the early modern aspects of the Renaissance and argues that it was a break from the past, but many historians today focus more on its medieval aspects and argue that it was an extension of the Middle Ages. However, the beginnings of the period – the early Renaissance of the 15th century and the Italian Proto-Renaissance from around 1250 or 1300 – overlap considerably with the Late Middle Ages, conventionally dated to c. 1250–1500, and the Middle Ages themselves were a long period filled with gradual changes, like the modern age; and as a transitional period between both, the Renaissance has close similarities to both, especially the late and early sub-periods of either.

The intellectual basis of the Renaissance was its version of humanism, derived from the concept of Roman humanitas and the rediscovery of classical Greek philosophy, such as that of Protagoras, who said that "man is the measure of all things". This new thinking became manifest in art, architecture, politics, science, and literature. Early examples were the development of perspective in oil painting and the revived knowledge of how to make concrete. Although the invention of metal movable type sped the dissemination of ideas from the later 15th century, the changes of the Renaissance were not uniform across Europe: the first traces appear in Italy as early as the late 13th century, in particular with the writings of Dante and the paintings of Giotto.

As a cultural movement, the Renaissance encompassed innovative flowering of Latin and vernacular literatures, beginning with the 14th-century resurgence of learning based on classical sources, which contemporaries credited to Petrarch; the development of linear perspective and other techniques of rendering a more natural reality in painting; and gradual but widespread educational reform. In politics, the Renaissance contributed to the development of the customs and conventions of diplomacy, and in science to an increased reliance on observation and inductive reasoning. Although the Renaissance saw revolutions in many intellectual and social scientific pursuits, as well as the introduction of modern banking and the field of accounting, it is perhaps best known for its artistic developments and the contributions of such polymaths as Leonardo da Vinci and Michelangelo, who inspired the term "Renaissance man".

The Renaissance began in Florence, one of the many states of Italy. Various theories have been proposed to account for its origins and characteristics, focusing on a variety of factors including the social and civic peculiarities of Florence at the time: its political structure, the patronage of its dominant family, the Medici, and the migration of Greek scholars and their texts to Italy following the fall of Constantinople to the Ottoman Turks. Other major centers were Venice, Genoa, Milan, Rome during the Renaissance Papacy, and Naples. From Italy, the Renaissance spread throughout Europe in Flanders, France, Britain, Ireland, Spain, Portugal, Germany, Poland, Hungary (with Beatrice of Naples), and elsewhere.

The Renaissance has a long and complex historiography, and in line with general scepticism of discrete periodizations, there has been much debate among historians reacting to the 19th-century glorification of the "Renaissance" and individual cultural heroes as "Renaissance men", questioning the usefulness of Renaissance as a term and as a historical delineation. Some observers have called into question whether the Renaissance was a cultural "advance" from the Middle Ages, instead seeing it as a period of pessimism and nostalgia for classical antiquity, while social and economic historians, especially of the longue durée, have instead focused on the continuity between the two eras, which are linked, as Panofsky observed, "by a thousand ties".

The term rinascita ('rebirth') first appeared in Giorgio Vasari's Lives of the Artists (c. 1550), anglicized as the Renaissance in the 1830s. The word has also been extended to other historical and cultural movements, such as the Carolingian Renaissance (8th and 9th centuries), Ottonian Renaissance (10th and 11th century), and the Renaissance of the 12th century.