El Dorado is a city and county seat of Butler County, Kansas, United States. It is situated along the Walnut River in the central part of Butler County and located in south-central Kansas. As of the 2020 census, the population of the city was 12,870. It is home to Butler Community College.

El Dorado Lake is a reservoir on the Walnut River 0.5 miles (0.80 km) northeast of El Dorado in the Flint Hills region of Kansas. Built and managed by the U.S. Army Corps of Engineers, it is used for flood control, recreation, and water supply. El Dorado State Park is located on its shore.