Lansing is a city in Leavenworth County, Kansas, United States. It is situated along the west side of the Missouri River and Kansas-Missouri state border. As of the 2020 census, the population of the city was 11,239. It is the second most populous city of Leavenworth County and is a part of the Kansas City metropolitan area. The Lansing Correctional Facility (formerly the Kansas State Penitentiary), which includes the state's main maximum-security prison, is located in Lansing.