A chanson (UK: /ˈʃɒ̃sɒ̃/, US: /ʃɑːnˈsɔːn/; French: chanson française [ʃɑ̃sɔ̃ fʁɑ̃sɛːz] ^ⓘ, lit. 'French song') is generally any lyric-driven French song. The term is most commonly used in English to refer either to the secular polyphonic French songs of late medieval and Renaissance music or to a specific style of French pop music which emerged in the 1950s and 1960s. The genre had origins in the monophonic songs of troubadours and trouvères, though the only polyphonic precedents were 16 works by Adam de la Halle and one by Jehan de Lescurel. Not until the ars nova composer Guillaume de Machaut did any composer write a significant number of polyphonic chansons.

A broad term, the word chanson literally means "song" in French and can thus less commonly refer to a variety of (usually secular) French genres throughout history. This includes the songs of chansonnier, chanson de geste and Grand chant; court songs of the late Renaissance and early Baroque music periods, air de cour; popular songs from the 17th to 19th century, bergerette, brunette, chanson pour boire, pastourelle, and vaudeville; art song of the romantic era, mélodie; and folk music, chanson populaire [fr]. Since the 1990s, the term may be used for Nouvelle Chanson, a French song that often contains poetic or political content.

The earliest chansons were the epic poems performed to simple monophonic melodies by a professional class of jongleurs or ménestrels. These usually recounted the famous deeds (geste) of past heroes, legendary and semi-historical. The Song of Roland is the most famous of these, but in general the chansons de geste are studied as literature since very little of their music survives.

The chanson courtoise or grand chant was an early form of monophonic chanson, the chief lyric poetic genre of the trouvères. It was an adaptation to Old French of the Occitan canso. It was practised in the 12th and 13th centuries. Thematically, as its name implies, it was a song of courtly love, written usually by a man to his noble lover. Some later chansons were polyphonic and some had refrains and were called chansons avec des refrains.

In its typical specialized usage, the word chanson refers to a polyphonic French song of the late Middle Ages and Renaissance. Early chansons tended to be in one of the formes fixes—ballade, rondeau or virelai (formerly the chanson baladée)—though some composers later set popular poetry in a variety of forms. The earliest chansons were for two, three or four voices, with first three becoming the norm, expanding to four voices by the 16th century. Sometimes, the singers were accompanied by instruments.

The first important composer of chansons was Guillaume de Machaut, who composed three-voice works in the formes fixes during the 14th century.

Two composers from Burgundy, Guillaume Du Fay and Gilles Binchois, who wrote so-called Burgundian chansons, dominated the subsequent generation of chanson composers (c. 1420–1470). Their chansons, while somewhat simple in style, are also generally in three voices with a structural tenor. These works are typically still 3 voices, with an active upper voice (discantus) pitched above two lower voices (tenor and altus) usually sharing the same range. Musicologist David Fallows includes the Burgundian repertoire in A Catalogue of Polyphonic Songs 1415–1480.

Later 15th- and early 16th-century figures in the genre included Johannes Ockeghem and Josquin des Prez, whose works cease to be constrained by formes fixes and begin to feature a pervading imitation (all voices sharing material and moving at similar speeds), similar to that found in contemporary motets and liturgical music. The first book of music printed from movable type was Harmonice Musices Odhecaton, a collection of ninety-six chansons by many composers, published in Venice in 1501 by Ottaviano Petrucci.