A virelai is a form of medieval French verse used often in poetry and music. It is one of the three formes fixes (the others were the ballade and the rondeau) and was one of the most common verse forms set to music in Europe from the late thirteenth to the fifteenth centuries.

One of the most famous composers of virelai is Guillaume de Machaut (c. 1300–1377), who also wrote his own verse; 33 separate compositions in the form survive by him. Other composers of virelai include Jehannot de l'Escurel, one of the earliest (d. 1304), and Guillaume Dufay (c. 1400–1474), one of the latest.

By the mid-15th century, the form had become largely divorced from music, and numerous examples of this form (including the ballade and the rondeau) were written, which were either not intended to be set to music, or for which the music has not survived.

A virelai with only a single stanza is also known as a bergerette.