St Patrick's Day - for many a chance to get dressed up in green and neck plenty of Guinness.
But what do you actually know about St Patrick himself?
Here are 12 facts about the man whose day it is today.
1. Patrick wasn’t his real name – it was Maewyn Succat.
2. He was captured by Irish raiders at the age of 16, and spent several years as a slave in Ireland.
3. During his 30 years there, he was pretty busy – he is said to have converted over 135,000 people, established 300 churches, and consecrated 350 bishops.
4. He learned all about the culture of the Druids, and converted them to Christianity.
5. Patrick is said to have had a dream where God spoke to him, saying ‘Your ship is ready.’ He then escaped Ireland by ship.
6. The dreams weren’t over yet – not long afterwards, he had another in which he received a letter that was labelled as ‘the voice of the Irish’. When he opened it, he heard the voices of everyone he had met in Ireland, begging him to return.
7. When he returned to Ireland to tell people about Christ, the Irish were responsive to his teachings, as he took several of their Celtic symbols and was able to ‘Christianise’ them.
8. The shamrock, which is the most well-known of Patrick’s illustrations, is a certain type of clover which is sacred to the Druids. Patrick used it as a symbol of the Trinity.
9. Green doesn’t just represent Irish culture – it symbolises spring, too.
10. The first St. Patrick Day’s parade in the US was held in New York on 17 March 1762, and consisted mainly of Irish soldiers.
11. Although it started out as a religious holiday, the day has become a general celebration of all things Irish.
12. St Patrick’s Day has been celebrated on 17 March for over a millennium.