Osceola County is a county located in the central portion of the U.S. state of Florida. As of the 2010 census, the population was 268,685. Its county seat is Kissimmee. Osceola County is included in the Orlando–Kissimmee–Sanford, Fla. Metropolitan Statistical Area. Osceola County is named for the Indian leader Osceola, whose name means “Black Drink Cry”.