Harvard Square is a triangular plaza at the intersection of Massachusetts Avenue, Brattle Street and John F. Kennedy Street near the center of Cambridge, Massachusetts, United States. The term "Harvard Square" is also used to delineate the business district and Harvard University surrounding that intersection, which is the historic center of Cambridge. Adjacent to Harvard Yard, the historic heart of Harvard University, the Square (as it is sometimes called, locally) functions as a commercial center for Harvard students, as well as residents of western Cambridge, the western and northern neighborhoods and the inner suburbs of Boston. The Square is served by Harvard station, a major MBTA Red Line subway and a bus transportation hub.

The name "Harvard Square" can also refer to the entire neighborhood surrounding this intersection for several blocks in each direction, including Brattle Square, a block away, and the nearby Cambridge Common. The Common is a park area with a playground, baseball field, and a number of monuments, several relating to the Revolutionary War.