Mari Lwyd is the Welsh midwinter tradition in which a decorated horse skull visits homes.
The Mari Lwyd is usually made from a horse skull mounted on a pole, covered with a white sheet, and decorated with ribbons, bells, and colored features. A group carries it from house to house during the Christmas and New Year season. At each home, participants traditionally exchange rhyming verses with the occupants in a playful contest called pwnco.
If the visiting party wins the verse exchange, the Mari Lwyd is allowed inside, and the group receives refreshments. The custom is associated especially with south Wales. Its exact origins are uncertain, and claims that it is definitely pre-Christian should be treated cautiously because surviving written evidence is later.
Mari Lwyd is not a Welsh version of Santa Claus. It is a community mumming and wassailing tradition, though both belong to the wider winter-season customs of Europe.