Cathlamet is a town located along the Ocean Beach Highway in Wahkiakum County, Washington, United States where it is the county seat. The population was 532 at the 2010 census, though it has an additional rural population outside of the town limits.
From time immemorial, Cathlamet was the largest, or one of the largest, villages of Columbia River Indians west of the Cascade Mountains. This village of cedar houses included 300-400 inhabitants when visited by Lewis and Clark.
In 1846, James Birnie became the first permanent white settler at Cathlamet, moving there after a career with the Hudson's Bay Company. He set up a trading post, remnants of which were reported still standing in 1906.