Union Square is a neighborhood in the southeastern part of Somerville, Massachusetts, United States. It is centered on Union Square proper, which is located at the intersection of Washington Street, Webster Avenue, and Somerville Avenue.

Somerville is a city located directly to the northwest of Boston, and north of Cambridge, in Middlesex County, Massachusetts, United States. As of the 2020 United States Census, the city had a total population of 81,045 people. With an area of 4.12 square miles (10.7 km2), the city has a density of 19,671/sq mi (7,595/km2), making it the most densely populated municipality in New England and the 19th most densely populated incorporated municipality in the country. Somerville was established as a town in 1842, when it was separated from Charlestown. In 2006, the city was named the best-run city in Massachusetts by The Boston Globe. In 1972, 2009, and 2015, the city received the All-America City Award. It is home to Tufts University, which has its campus along the Somerville and Medford border.