
Sankt Patricks dag, forkortet Skt. Patricks dag (irsk: Lá Fhéile Pádraig), er en religiøs og kulturel helligdag, der afholdes d. 17. marts, der er den traditionelle dødsdag for skt. Patrick (ca. 385-461), og Irlands fremmeste skytshelgen.
Skt Patricks dag blev gjort til en officiel kristen helgendag i 1600-tallet, og den afholdes i den romerskkatolske krike, Den anglikanske kirke (særligt Church of Ireland), og ortodokse kirke og den lutheranske kirke. Dagens mindste sankt Patrick, og Kristendommens ankomst til Irland, og derudover fejrer den irske kultr og kulturarv generelt. Fejringer involverer offentlige parader og festivaller, céilithe, og folk er iført grønt tøj eller er dekoreret med shamrock. Det fejres særligt på irske pubber. Nogle kristne går også til gudstjenester. Historisk har fasteregler for indtagelse af mad og alkohol været ophævet denne dag, hvilket har gjort helligdagens ofte løssupne fester mulige.

Skt. Patricks dag er en offentlig helligdag og nationaldag i Irland, Nordirland, den canadiske provins Newfoundland and Labrador (for statsansatte), og for Storbritanniens oversøiske territorium Montserrat. Dagen bliver dog også fejret steder med mange irske emmigranter eller efterkommere af irere som Storbritannien, Canada, USA, Australien, New Zealand og South Africa. Skt. Patricks dag bliver fejret i flere lande end nogen anden nationaldag. Moderne fejringer er blevet meget påvirket af irske emmigranter, særligt dem der blev udviklet i Nordamerika. Der har dog også været kritik af Skt. Patricks dag-fejringerne for at være blevet for kommercieliserede og for at give negative stereotyper associationer til irlændere.
The day of celebration, which marks the day of St Patrick’s death, is a religious holiday meant to celebrate the arrival of Christianity in Ireland, and made official by the Catholic Church in the early 17th century. Observed by the Catholic Church, the Anglican Communion, the Eastern Orthodox Church, and the Lutheran Church, the day was typically observed with services, feasts and alcohol.
In nineteenth-century America it became a celebration of Irishness, more than a religious occasion, though attending Mass continues as an essential part of the day.
The religious occasion did involve the wearing of shamrocks, an Irish symbol of the Holy Trinity, and the lifting of Lenten restrictions on drinking.
For most Irish-Americans, this holiday (from holy day) is partially religious but overwhelmingly festive. For most Irish people in Ireland the day has little to do with religion at all and St. Patrick's Day church services are followed by parades and parties, the latter being the best attended. The festivities are marked by Irish music, songs, and dances.
Like many other forms of carnival, St. Patrick's Day is a feast day, a break from Lent in which adherents are allowed to temporarily abandon rigorous fasting by indulging the forbidden. Since alcohol is often proscribed during Lent the copious consumption of alcohol is seen as an integral part of St. Patrick's day.
The 40-day period (not counting Sundays) prior to Easter is known as Lent, a time of prayer and fasting. Pastors of Irish-American parishes often supplied "dispensations" for St. Patrick s Day, enabling parishioners to forego Lenten sacrifices in order to celebrate the feast of their patron saint.
There is only one place outside of Ireland that celebrates St. Patrick's Day as a national public holiday: the island of Montserrat. The small pear-shaped island is about 40 square miles and is located just south of Antigua. It's known as the Emerald Isle of the Caribbean.