Pittsburg County is a county located in the U.S. state of Oklahoma. As of the 2020 census, the population was 43,773. Its county seat is McAlester. The county was formed from part of the Choctaw Nation in Indian Territory in 1907. County leaders believed that its coal production compared favorably with Pittsburgh, Pennsylvania at the time of statehood.

McAlester is the county seat of Pittsburg County, Oklahoma. The population was 18,363 at the time of the 2010 census, a 3.4 percent increase from 17,783 at the 2000 census. The town gets its name from James Jackson McAlester, an early white settler and businessman who later became lieutenant governor of Oklahoma. Known as "J. J.", McAlester married Rebecca Burney, the daughter of a full-blood Chickasaw family, which made him a citizen of the Chickasaw Nation.