Wasco County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 25,213. Its county seat is The Dalles. The county is named for a local tribe of Native Americans, the Wasco, a Chinook tribe who live on the south side of the Columbia River. It is near the Washington state line. Wasco County comprises The Dalles Micropolitan Statistical Area.

The Dalles, formally the City of The Dalles and also called Dalles City, is an inland port and the largest city in Wasco County, Oregon, United States. The population was 16,010 at the 2020 census, and it is the largest city in Oregon along the Columbia River outside the Portland Metropolitan Area. The Dalles is 75 miles east of Portland, within the Columbia River Gorge National Scenic Area.