Marblemount is a census-designated place in Skagit County, Washington, United States. The population was 286 at the 2020 census. It is included in the Mount Vernon–Anacortes, Washington Metropolitan Statistical Area.

Skagit County is a county in the U.S. state of Washington. As of the 2020 census, the population was 129,523. The county seat and largest city is Mount Vernon. The county was formed in 1883 from Whatcom County and is named for the Skagit Indian tribe, which has been indigenous to the area prior to European-American settlement.