Saint Patrick's Day is celebrated worldwide by the those of Irish descent and increasingly by non-Irish people (usually in New Zealand, Australia, and North America). Celebrations are generally themed around all things Irish and, by association, the colour green. Both Christians and non-Christians celebrate the secular version of the holiday by wearing green, eating Irish food and/or green foods, imbibing Irish drink (such as Irish stout, especially Guiness, Irish Whiskey or Irish Cream) and attending parades.

Saint Patrick's Day parades have a long history in North America. The Irish Society of Boston organized what was apparently the first Saint Patrick's Day Parade in the colonies on 17 March, 1737.^{[5][unreliable source?]} Other sources cite later parades as the first. For instance, ^{some who?]} claim that the world's first St. Patrick's Day parade (not just the first in the Colonies) was held in Boston in 1761, organized by the Charitable Society. citation ^needed] There is a competing claim that the first recorded parade^[6] was New York City's celebration which began on 18 March, 1762 when Irish soldiers in the English military marched through the city with their music.^[7] The New York parade is the largest, typically drawing two million spectators and 150,000 marchers.^[8] The Canadian city of Montreal, in the predominantly French-speaking province of Québec has the longest continually running Saint Patrick's day parade in North America, since 1824;^[9] The city's flag has the Irish emblem, the shamrock, in one of its corners. Ireland's cities all hold their own parades and festivals, including Dublin, Cork, Belfast, Derry, Galway, Kilkenny, Limerick, and Waterford. Parades also take place in other Irish towns and villages. The St. Patrick's Day parade in Dublin, Ireland is part of a five-day festival; over 675,000 people attended the 2009 parade.