Riley County is a county located in the U.S. state of Kansas. Its county seat and largest city is Manhattan. As of the 2020 census, the population was 71,959. The county was named after Bennet Riley, the 7th governor of California, and a Mexican–American War hero. Riley County is home to Fort Riley and Kansas State University.

Manhattan is a city in and the county seat of Riley County, Kansas, U.S., although the city extends into Pottawatomie County. It is located in northeastern Kansas at the junction of the Kansas River and Big Blue River. As of the 2020 Census, the population of the city was 54,100.