Chehalis is a city in and the county seat of Lewis County, Washington, United States. The population was 7,439 at the time of the 2020 census. The city is located in the Chehalis valley and is split by Interstate 5 and State Route 6. It is twinned with the bordering city of Centralia. The communities of Napavine and Newaukum lie directly south, with the town of Adna to the west.