Chelmsford High School is a public high school founded in 1917. The current building is located in North Chelmsford, Massachusetts, United States, and was built in 1974. Before 1974 the high school was located in the current McCarthy Middle School building. It serves as the public high school for students in grades 9–12 and has been ranked among the top 500 schools in the nation by Newsweek.

It is part of a central campus that includes four of the town's seven schools. The three other schools at the central campus are the C. Edith McCarthy Middle School, the Col. Moses S. Parker Middle School and the Charles D. Harrington Elementary School.