Coos Bay is a city located in Coos County, Oregon, United States, where the Coos River enters Coos Bay on the Pacific Ocean. The city borders the city of North Bend, and together they are often referred to as one entity called either Coos Bay-North Bend or Oregon's Bay Area. Coos Bay's population as of the 2020 census was 15,985 residents, making it the most populous city on the Oregon Coast. Oregon's Bay Area is estimated to be home to 32,308.

Coos County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 64,929. The county seat is Coquille. The county was formed from the western parts of Umpqua and Jackson counties. It is named after a tribe of Native Americans who live in the region. Coos County comprises the Coos Bay, OR Micropolitan Statistical Area.