Mercer Island High School (MIHS) is a public high school located in Mercer Island, Washington in the U.S., as part of the Mercer Island School District.

As of the 2005-06 school year, the school had an enrollment of 1,460 students and 67.2 classroom teachers (on an FTE basis), for a student-teacher ratio of 21.7. detail.asp?Search=1&DistrictID=5304980&ID=530498000761" target="_blank">Mercer Island High School, _National Center for Education Statistics. Accessed November 1, 2007.