Thousands of people celebrated St Patrick's Day or "The fest of St Patrick" in a colourful way in the island of Ireland to honour his role in bringing Catholicism to the country.

The celebrations are held every year on the 17th of March which is thought to be the date St Patrick died.

Not only is the celebration marked in Ireland, it is celebrated across the world by the Irish diaspora. And many who are not Irish or Catholic often join in the festivities, including the British Royal family.

In the US city of Chicago, the Chicago River was dyed a bright shade of green, kicking off the city's St. Patrick's Day festivities.

Thousands of people lined the riverfront downtown Chicago on Saturday to see the dyeing, a tradition for the holiday that dates to 1962.

A parade was also scheduled.

And of course, celebrations took place in New York, with Ireland's Prime Minister Leo Varadkar taking part in that city's St Patrick's Day parade.