Douglas County is a county located in the U.S. state of Nebraska. As of the 2020 United States Census, the population is 584,526. It is the state's most populous county, home to just under 30% of Nebraska's residents. Its county seat is Omaha, the state's largest city. The county was established in 1854 and named after Stephen A. Douglas, who was then serving as a U.S. senator from Illinois. Douglas County is part of the Omaha-Council Bluffs, NE-IA Metropolitan Statistical Area.