Acton-Boxborough Regional High School (ABRHS or simply AB) is an open-enrollment high school in Acton, Massachusetts, United States.

A part of the Acton-Boxborough Regional School District, it serves the Massachusetts towns of Acton and Boxborough and has students in grades 9 through 12.

It is situated downhill from the Raymond J. Grey Junior High School, at 36 Charter Road in Acton.

The second fire, a five-alarm blaze in the school auditorium, seriously damaged the auditorium and forced the evacuation of all 1,300 students and canceled school the following day.

No students or staff were injured, but one firefighter was hospitalized after suffering from smoke inhalation.