The Oklahoma State Penitentiary, nicknamed "Big Mac", is a prison of the Oklahoma Department of Corrections located in McAlester, Oklahoma, on 1,556 acres (6.30 km²). Opened in 1908 with 50 inmates in makeshift facilities, today the prison holds more than 750 male offenders, the vast majority of which are maximum-security inmates. They also hold many death row prisoners.

Before Oklahoma became a state in 1907, felons convicted in Oklahoma Territory and Indian Territory were sent to the Kansas State Penitentiary in Lansing, Kansas. At statehood, Kate Barnard became Oklahoma Commissioner of Charities and Corrections. During the summer of 1908, Barnard arrived unannounced at the Kansas prison to investigate widespread complaints she had received about mistreatment of Oklahoma inmates. She took a regular tour with other visitors first, then identified herself to prison officials and asked that she be allowed to conduct an inspection of the facility. Barnard discovered systematic, widespread torture of inmates.

Upon her return to Oklahoma, Barnard recommended that all Oklahoma inmates be removed from the Lansing facility and returned to the state. Governor of Oklahoma Charles N. Haskell supported Barnard's proposal, and within two months of Barnard's visit to Kansas, on October 14, 1908, two groups of 50 offenders each were sent by train to McAlester. The inmates were temporarily housed in the former federal jail in the town. Under direction from Warden Robert W. Dick, they built a stockade to house themselves on a 120 acres (0.49 km²) plot northwest of McAlester, which was donated to the state by a group of McAlester citizens.

The remaining Oklahoma inmates in Lansing were moved to the United States Penitentiary, Leavenworth until the state could build adequate facilities to house them all. The next spring, in 1909, the Oklahoma Legislature appropriated $850,000 to build the permanent facility.

Construction began in May 1909 on a prison designed after the Leavenworth facility. The state purchased about 1,556 acres (6.30 km²) surrounding the original plot of land. Using prison labor, the West Cellhouse and Administration Building were completed first; the Rotunda and East Cellhouse came later. The steep hills and grades required more than 6,250 cubic yards (4,780 m³) of concrete and more than 2,000,000 cubic yards (1,500,000 m³) of rocks and soil to be moved for the prison's walls alone. The F Cellhouse was added in 1935, and later the New Cellhouse was constructed. A shoe manufacturing plant and a tailor shop were part of the prison's inmate industry program, designed to provide work for offenders; at Lansing, prisoners were forced to work in the local mines, a practice Barnard banned. The Warden's House, across the street from the prison, is listed on the National Register of Historic Places.

Female prisoners were sent to Kansas in territorial days also. The first females brought back from Kansas stayed in a ward near the East Gate, built in 1911, on the fourth floor of the West Cellhouse. The female population had grown to 26 by the time a separate building about 1 mile (1.6 km) west of the main institution was completed in 1926.

The Talawanda Heights Minimum Security Unit was opened outside the East Gate Area in October 1989 to house inmates who hold support jobs inside the facility. In 1992, a special care unit opened to provide mental health care to offenders, reducing the need for psychiatric hospitalization outside the prison. A medium security unit with a capacity of 140 inmates is located on G and I units to help prisoners adjust to a lower security classification.

Another addition to the prison, H Unit, houses inmates under both administrative and disciplinary segregation. H Unit is also the site of Oklahoma's death row and the state's lethal injection death chamber.