Montgomery Blair High School (MBHS) is a public high school located in Silver Spring, Maryland, United States, operated by Montgomery County Public Schools. The school's total enrollment of 3,200 makes it the largest public high school in Montgomery County and Maryland as a whole.

The school was named after Montgomery Blair, a lawyer who represented Dred Scott in his Supreme Court case, and later served as Postmaster General under President Abraham Lincoln. After opening in 1925 as Takoma Park-Silver Spring High School, the Blair name was adopted in 1935 when the school moved to a location overlooking Sligo Creek at 313 Wayne Avenue. In 1998, the campus moved again two miles (3 km) north to the Kay Tract, a long-vacant site adjacent to the Capital Beltway, and the old building was repurposed to house Silver Spring International Middle School and Sligo Creek Elementary School.

About 20% of the student body is part of one of two magnet programs: the Science, Math, and Computer Science Magnet, and the Communication Arts Program (CAP), which draw students from both the Silver Spring area and across Montgomery County. It is a member of the National Consortium for Specialized Secondary Schools of Mathematics, Science and Technology (NCSSSMST).

Prior to the 2010 U.S. Census the school was within the Silver Spring census-designated place, but as of 2015 it now resides in the Four Corners CDP.