"Sumer Is Icumen In" (also called the Summer Canon and the Cuckoo Song) is a medieval English round or rota of the mid-13th century.
The title translates approximately to "Summer Has Come In" or "Summer Has Arrived". The song is composed in the Wessex dialect of Middle English. Although the composer's identity is unknown today, it may have been W. de Wycombe. The manuscript in which it is preserved was copied between 1261 and 1264.
This rota is the oldest known musical composition featuring six-part polyphony.