Tecumseh is a city in Pottawatomie County, Oklahoma, United States. The population was 6,457 at the 2010 census, a 5.9 percent increase from 6,098 at the 2000 census. It was named for the noted Shawnee chief, Tecumseh, and was designated as the county seat at Oklahoma's statehood. A county-wide election moved the seat to Shawnee in 1930.