Osceola County is a county located in the U.S. state of Iowa. As of the 2020 census the population was 6,192, making it the state's fifth-least populous county. It is named for Seminole war chief Osceola. The county seat is Sibley, named for H. H. Sibley of Minnesota.

Osceola, named Billy Powell at birth in Alabama, became an influential leader of the Seminole people in Florida. His mother was Muscogee, and his great-grandfather was a Scotsman, James McQueen. He was reared by his mother in the Creek (Muscogee) tradition. When he was a child, they migrated to Florida with other Red Stick refugees, led by a relative, Peter McQueen, after their group's defeat in 1814 in the Creek Wars. There they became part of what was known as the Seminole people.