The Harvard Extension School, founded by Harvard University President A. Lawrence Lowell in 1909, is an academic evening program designed to serve the educational interests and needs of the greater Boston community. The Extension School features open enrollment, part-time evening classes, coeducation, instructors drawn mainly from Harvard, and an opportunity for personal enrichment, career advancement, or study leading to a degree or certificate. The school currently awards the degrees of associate in art (AA), bachelor of liberal arts (ALB), master of liberal arts (MLA), master of liberal arts in mathematics for teaching, and master of liberal arts in information technology. There are certificate programs in administration and management, applied sciences, environmental management, publishing and communications, and technologies of education.

The Extension School is part of the Division of Continuing Education, which itself is part of the Harvard Faculty of Arts and Sciences.