The United States Disciplinary Barracks (USDB), sometimes simply called Leavenworth, confines Army, Air Force, Navy, Marine Corps and Coast Guard offenders. USDB is located at Fort Leavenworth, Kansas near the cities of Leavenworth and Lansing. Leavenworth is a maximum-security prison for commissioned officers, national-security related offenders convicted by court martial and any prisoners serving long sentences.

The Fort Leavenworth location was originally known as the United States Military Prison, and was established by the United States Congress in 1874. It has been in continuous operation since May 15, 1875, with a new 521-bed facility put into use in 2002.

The historic confinement building, known as "the Castle", was built by the convicts and completed in 1921. It housed up to 1,500 prisoners. Demolition of the Castle started in 2004 and was expected to take about one year. There is a cemetery on the grounds, the Fort Leavenworth Military Prison Cemetery, which saw its last burial in 1957.

USDB was the first prison in the nation to offer vocational training for prisoners.

The last execution at the prison was Army Pfc. John A. Bennett, who was executed by hanging on April 13, 1961; his was also the most recent execution conducted by the United States Armed Forces.