Cottage Grove is a city in Lane County, Oregon, United States. Its population was 10,643 at the 2020 census. It is the third largest city in Lane County. It is on Interstate 5, Oregon Route 99, and the main Willamette Valley line of the CORP railroad.

Lane County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 382,971, making it the fourth-most populous county in Oregon. The county seat is Eugene, the state's second most populous city. It is named in honor of Joseph Lane, Oregon's first territorial governor.