The Isaac Fay House is an historic house at 125 Antrim Street in Cambridge, Massachusetts. The 2.5 story wood frame house was built in 1843, and is one of the city's best examples of a Greek Revival side-hall plan. It also has distinctive features, including a cupola and an Ionic wraparound porch, that are not found on any surviving period building in the city. The house was originally located on Fayette Street, and was moved to its present location in 1856. It belonged to Isaac Fay, a city alderman.