Patriots' Day (officially Patriots' Day in Massachusetts and Patriot's Day in Maine) is a civic holiday commemorating the anniversary of the Battles of Lexington and Concord, the first battles of the American Revolutionary War. It is observed on the third Monday in April in Massachusetts and Maine (once part of Massachusetts), and is a public school observance day in Wisconsin. Observances and re-enactments of these first battles of the American Revolution occur annually at Lexington Green in Lexington, Massachusetts, (around 6:00 am) and The Old North Bridge in Concord, Massachusetts, (around 9:00 am). In the morning, mounted re-enactors with state police escorts retrace the rides of Paul Revere and William Dawes, calling out warnings the whole way.

Since 1969, the holiday has been observed on the third Monday in April, providing a three-day long weekend, as well as being the first day of public school vacation week in Maine and Massachusetts. Previously, it had been designated as April 19 in observance of the anniversary of the Battles of Lexington and Concord, the first battles of the American Revolutionary War. It is also a school holiday for many local colleges and universities, both public and private.