Washington's 10th congressional district is a congressional district in western Washington. The district is centered on the state capital, Olympia, and includes portions of Thurston and Pierce counties. It was created after the 2010 United States census, which granted Washington an additional congressional seat, bringing the number of seats apportioned to the state up from 9 to 10, and elected Denny Heck as its first member to the United States House of Representatives in the 2012 elections. Marilyn Strickland was elected in 2020 to replace him after he retired to run for Lieutenant Governor.

Thurston County is a county located in the U.S. state of Washington. As of the 2020 census, its population was 294,793. The county seat and largest city is Olympia, the state capital.