Osawatomie State Hospital is a public psychiatric hospital in the U.S. state of Kansas, located in the city of Osawatomie, Kansas. Established by the Kansas legislature in 1863 and opened in 1866, it is the oldest operating psychiatric hospital in the state of Kansas. It has been named "Kansas Insane Asylum" and the "State Insane Asylum" but was officially changed to its present name in 1901.

Osawatomie is a city in Miami County, Kansas, United States, 61 miles (98 km) southwest of Kansas City. As of the 2020 census, the population of the city was 4,255. It derives its name as a portmanteau of two nearby streams, the Marais des Cygnes River and Pottawatomie Creek.