Cnapan (sometimes spelt Knapan or Knappan) is a Celtic form of medieval football, vaguely resembling some modern versions of rugby football, played in Wales until the nineteenth century. The game originated in, and seems to have remained largely confined to, the western counties of Wales, especially Carmarthenshire, Ceredigion and Pembrokeshire. According to George Owen of Henllys, in his Description of Pembrokeshire (1603), cnapan had been "extremely popular in Pembrokeshire since greate antiquitie [sic]".

Little information is known about the origins of cnapan, due to the age of the game, but it seems to have originated sometime in the Middle Ages as a form of "organised chaos", to relieve the back-breaking monotonous work of daily life. George Owen of Henllys says, in his Description of Pembrokeshire (1603), that it had been a form of war training for the "Ancient Britons", used to improve strength and stamina. The game also seems to have evolved gradually over the years, with no definitive set of rules governing its play; but as the game is played with but a few simple rules, this has not been a major hindrance to play. Welsh clergyman and historian, Theophilus Evans (1693–1767), tells of a game similar to cnapan being played on the banks of the River Teifi; the ancient boundary between the counties of Ceredigion and Carmarthenshire, southwest Wales. Leaving aside the gentry on horseback, there were certainly two groups of players on each side, some who grappled for the cnapan (ball) and others who were the fastest and most elusive runners. There were also features approximating to scrummages and lineouts. The game died out in the nineteenth century, as the codified game of rugby union became popular.