Tumwater is a city located in Thurston County, Washington, in the United States. It serves as the southern gateway to the broader Seattle and Tacoma urban area, which extends from Tumwater to Marysville along the Interstate 5 corridor.
The city is situated near the point where the Deschutes River enters Budd Inlet, which marks the southernmost point of Puget Sound. It borders the state capital of Olympia to the north. Notably, Tumwater holds the distinction of being the oldest permanent Anglo-American settlement on Puget Sound. As of the 2020 census, the city had a population of 25,350.