Gardner is a city in Johnson County, Kansas, United States. As of the 2020 census, the population of the city was 23,287. It is located within the Kansas City metropolitan area.

Johnson County is a county in the U.S. state of Kansas, along the border of the state of Missouri. Its county seat is Olathe. As of the 2020 census, the population was 609,863, the most populous county in Kansas. The county was named after Thomas Johnson, a Methodist missionary who was one of the state's first settlers. Largely suburban, the county contains a number of suburbs of Kansas City, Missouri, including Overland Park, a principal city of and second most populous city in the Kansas City Metropolitan Area.