Brown County is a county located in the northeast portion of the U.S. state of Kansas. Its county seat and most populous city is Hiawatha. As of the 2020 census, the county population was 9,508. The county was named after Albert G. Brown, a U.S. Senator from Mississippi and Kansas statehood advocate. The Kickapoo Indian Reservation of Kansas, the majority of the Sac and Fox Reservation, and the majority of the Iowa Reservation of Kansas and Nebraska are located within the county.

Albert Gallatin Brown was Governor of Mississippi from 1844 to 1848 and a Democratic United States Senator from Mississippi from 1854 to 1861, when he withdrew during secession.