Lamar is the home rule municipality that is the county seat and the most populous municipality of Prowers County, Colorado. The city population was 7,687 at the 2020 United States Census. The city was named after L.Q.C. Lamar, a slaveholder, Confederate soldier and diplomat who wrote the Mississippi Secession Ordinance, and after the Civil War, went on to serve as Secretary of the Interior and as a Supreme Court Justice. Lamar is the home of Lamar Community College, and is the largest city in southeastern Colorado.

Prowers County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 11,999. The county seat is Lamar. The county is named in honor of John Wesley Prowers, a leading pioneer in the lower Arkansas River valley region.