Mountainside High School (MHS) is a public high school in Beaverton, Oregon.

In 2014, a $680 million bond measure was passed which would help fund 27 projects in the Beaverton School District.

[4] The school opened on September 5, 2017 as an orientation day for ninth grade students, with tenth grade students beginning the following day.

The neighborhood to the west of the school had previously been part of the Hillsboro School District, but this was changed upon the opening of MHS.

[9] Mountainside High School athletic teams compete in the OSAA 6A-2 Metro League, along with the other Beaverton schools.