Saint Patrick's Day, or the Feast of Saint Patrick, is a cultural and religious celebration held on 17 March, the traditional death date of Saint Patrick (c. AD 385–461), the foremost patron saint of Ireland.

Saint Patrick's Day was made an official Christian feast day in the early 17th century and is observed by the Catholic Church, the Anglican Communion (especially the Church of Ireland), the Eastern Orthodox Church, and the Lutheran Church.

The day commemorates Saint Patrick and the arrival of Christianity in Ireland, and celebrates the heritage and culture of the Irish in general.