Monrovia High School is a public high school located in Monrovia, California, a northeastern suburb of Los Angeles, United States. Monrovia High School is the only grades 9–12 comprehensive high school in the Monrovia Unified School District. Established in 1893, the campus is located in an environment of neo-Spanish architecture, green lawns, and hundred-year-old oak trees, and is nestled against the San Gabriel Mountains. The portion of the campus designed in 1928 is the work of noted Los Angeles architect John C. Austin.

In 2006, the citizens of Monrovia approved a $45 million bond for the high school. Major construction transformed the campus by adding a science building with technology labs, a gymnasium to support the physical education and sports programs, a stadium and bleachers, and an overall renovation of the campus. The construction was completed in 2012