Green ribbons and shamrocks were worn in celebration of St Patrick's Day as early as the 17th century. Saint Patrick's Day is celebrated worldwide by those of Irish descent and increasingly by people of other ethnicities as well. As well as being a celebration of Irish culture, Saint Patrick's Day is a Christian festival. The day almost always falls in the season of Lent, and some bishops will grant an indult, or release, from the Friday no-meat observance when St. Patrick's Day falls on a Friday; this is sometimes colloquially known as a "corned-beef indult".

Today, Saint Patrick's Day is widely celebrated in America by Irish and non-Irish alike. Many people, regardless of ethnic background, wear green-coloured clothing and items. Traditionally, those who are caught not wearing green are pinched, usually affectionately.