The Gilbrae Inn is a historic residential building at 403 River Street in Waltham, Massachusetts. It was built as a two-story wood frame structure by the Boston Manufacturing Company sometime between 1827 and 1854 as a boarding house for its workers. In c. 1870 the mansard roof and third floor were added. It is the only known surviving boarding house built by the company. Its name derives from a cloth pattern manufactured by the company.