Oklahoma State University–Stillwater is a public land-grant research university in Stillwater, Oklahoma. OSU was founded in 1890 under the Morrill Act. Originally known as Oklahoma Agricultural and Mechanical College, it is the flagship institution of the Oklahoma State University System that enrolls more than 34,000 students across its five institutions with an annual budget of $1.69 billion for fiscal year 2024. As of Fall 2023, 26,008 students are enrolled at the university. OSU is classified among "R1: Doctoral Universities – Very high research activity". According to the National Science Foundation, OSU spent $198.8 million on research and development in 2021.

Stillwater is the tenth-largest city in the U.S. state of Oklahoma. It is the county seat of Payne County, Oklahoma. It is located in north-central Oklahoma at the intersection of U.S. Route 177 and State Highway 51. As of the 2020 census, the city population was 48,394. The Stillwater Micropolitan Statistical Area had a population of 78,399 according to the 2012 census estimate. Stillwater was part of the first Oklahoma Land Run held on April 22, 1889, when the Unassigned Lands were opened for settlement and became the core of the new Oklahoma Territory. The city charter was adopted on August 24, 1889, and operates under a council-manager government system.