Saint David's Day (Welsh: Dydd Gŵyl Dewi Sant - "Day of the Festival of Saint David") is the day that the patron saint of Wales, Saint David, is celebrated. It falls on 1 March every year.

Children wear Welsh costumes and take part in school concerts or eisteddfodau, with recitation and singing being the main activities. Formerly, a half-day holiday was afforded to school children. Officially this custom does not continue, although the practice can vary on a school-to-school basis.

Many Welsh people wear one or both of the national emblems of Wales on their lapel to celebrate Saint David: the daffodil (a generic Welsh symbol which is in season during March) or the leek (Saint David's personal symbol) on this day. The association between leeks and daffodils is strengthened by the fact that they have similar names in Welsh, Cenhinen (leek) and Cenhinen Bedr (daffodil, lit. "Peter's leek").