St. David's Day is a Christian feast day celebrated annually on March 1 in honor of Saint David, the patron saint of Wales ("Dewi Sant" in Welsh), who is said to have died on March 1, 589, though that date is not certain.

David was a native of Wales and a member of the royal family of Cunedda. He rose to fame as archbishop and founder of a number of monasteries.

On St. David's Day daffodils and leeks, the national emblems of Wales, are worn, in a tribute to Saint David who is said to have eaten only leeks when fasting and to have advised soldiers to wear leeks on their helmets in a battle against Saxons so they could distinguish each other from the enemies. Cities and towns in Wales hold parades on the day, flying the Welsh flag (or alternatively the flag of Saint David, a yellow cross on a black field) and displaying dragons, another symbol of Wales. Recitations and choir singing is performed, and the national anthem is played.

St. David's Day, also spelled Saint David's Day, is not a public holiday in Wales. It is one of the four Saints' days of the four nations that make up the United Kingdom.