St Patrick’s Day Aka the Feast of Saint Patrick, this is a Christian feast day and cultural holiday in celebration of Saint Patrick, patron saint of Ireland. It is a public holiday in the Republic of Ireland, Northern Ireland, some Canadian provinces and the British Overseas Territory of Montserrat. St Patrick’s Day is widely and informally celebrated in the UK, Canada, US, Argentina, Australia and New Zealand. Popular customs include wearing green, drinking beer (at Irish pubs, if possible) and revelling. Many famous landmarks across the world, including the Sydney Opera House, have joined the celebration by lighting up in green.