Washington County is a county in the U.S. state of Minnesota. As of the 2020 census, the population was 267,568, making it the fifth-most populous county in Minnesota. Its county seat is Stillwater. The largest city in the county is Woodbury, the eighth-largest city in Minnesota and the fourth-largest Twin Cities suburb.

Stillwater is a city in the U.S. state of Minnesota and the county seat of Washington County. It is in the Minneapolis–Saint Paul metropolitan area, on the west bank of the St. Croix River, across from Houlton, Wisconsin. Stillwater's population was 19,394 at the 2020 census. Stillwater is often called "the birthplace of Minnesota" due to its role in the establishment of the state.