Clatsop County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 41,072. The county seat is Astoria. The county is named for the Clatsop tribe of Native Americans, who lived along the coast of the Pacific Ocean prior to European settlement. Clatsop County comprises the Astoria, OR Micropolitan Statistical Area, or Sunset Empire, and is located in Northwest Oregon.

Astoria is a port city and the seat of Clatsop County, Oregon, United States. Founded in 1811, Astoria is the oldest city in the state and was the first permanent American settlement west of the Rocky Mountains. The county is the northwest corner of Oregon, and Astoria is located on the south shore of the Columbia River, where the river flows into the Pacific Ocean. The city is named for John Jacob Astor, an investor and entrepreneur from New York City, whose American Fur Company founded Fort Astoria at the site and established a monopoly in the fur trade in the early 19th century. Astoria was incorporated by the Oregon Legislative Assembly on October 20, 1856.