Marked every year on 17 March, it is an occasion to mark Ireland’s patron saint with shamrocks, parades and copious amounts of Guinness.

St Patrick is famous for driving snakes from Ireland, but what else did he do to achieve such prominence? Here’s everything you need to know.

Where was St Patrick from?

Born at the end of the fourth century in Roman Britain, he was the grandson of a priest – though was not particularly devout as a boy.

His life changed at the age of sixteen when he was kidnapped by raiders and taken to Ireland as a slave.

The saint spent six years working as a shepherd and praying, developing a deeper relationship with God, until one day he was said have heard a voice.

“Look – your ship is ready,” it said, according to the account of the saint himself in his “Confession”, which tells his early life story.

Fleeing his master, he found a ship to take him back to Britain, where he returned to his family and continued to study Christianity there and in France.

Then came a vision in which a horde of Irish appeared to him and said: “We appeal to you, holy servant boy, to come and walk among us.”

What did St Patrick do in Ireland?

He headed to Ireland again, this time as a missionary. His arrival is dated to 432 AD, and marks a major moment in Irish history. He set about converting the previously pagan, druidic island to Christianity with remarkable success.

Soon after, a monastic system on the continental model popped up in Ireland, and the country became literate, writing in Latin and then in Irish using the Latin alphabet.

Ireland can claim the longest unbroken written record in Europe, stretching through the Dark Ages.

Folk stories say Patrick founded 300 churches and converted 100,000 people.

He’s generally associated with the northern half of the island, and specifically Armagh – where the most senior Catholic and Anglican bishops are based – and Downpatrick, where he is said to be buried.

How did St Patrick drive the snakes from Ireland?

The main miracle associated with St Patrick, and taught to all schoolchildren, is driving the snakes out of Ireland.

Attacked by some serpents while undergoing a 40-day fast on a hill, he drove his staff into the ground and sent them (and all other snakes in the country) into the sea.

As a result, unsurprisingly, he’s often invoked against snakes. There are no native snakes in Ireland to this day, but that could be to do with the climate and the vagaries of the Ice Age thaw.

What is St Patrick the patron saint of?

St Patrick is the patron saint of Nigeria, Puerto Rico, Boston, engineers and – most commonly in the public consciousness – Ireland, and he is commemorated across the world.

His life has been been celebrated since the 1700s in parts of the United States, which has long drawn emigrants from Ireland.

New York’s parade is the biggest on earth, with two million people lining midtown Manhattan to watch on.

In Ireland, every town usually has a parade, and the main parade in Dublin is televised live, with a million people taking part in long-weekend festivities.

Malta has a long tradition of celebrating, initiated by a regiment of Royal Dublin Fusiliers in the early 20th century, while Argentina’s unofficial parade attracts 20,000 revellers to a neighbourhood with several Irish bars in Buenos Aires.

The furthest celebrations afield, however, took place in 2011, when Irish-American astronaut Catherine Molloy played a 100-year-old Irish flute aboard the International Space Station to mark the day.