Tuol Sleng Genocide Museum

Tuol Sleng
Former school used as killing field by the Santebal
The exterior of the Tuol Sleng Genocide Museum, Phnom Penh
Location of Tuol Sleng within Cambodia
Coordinates	11°32′58″N 104°55′04″E / 11.54944°N 104.91778°E / 11.54944; 104.91778Coordinates: 11°32′58″N 104°55′04″E / 11.54944°N 104.91778°E / 11.54944; 104.91778
Other names	S-21
Known for	Internment and extermination camp used by the Khmer Rouge
Location	Phnom Penh
Operated by	Khmer Rouge
Commandant	Kang Kek Iew
Original use	High school
Operational	1975–1979
Number of inmates	~20.000 prisoners
Killed	~20.000
Liberated by	People's Army of Vietnam
Notable inmates	Chum Mey
Website	Tuol Sleng genocide museum

The Tuol Sleng Genocide Museum (Khmer: សារមន្ទីរឧក្រិដ្ឋកម្មប្រល័យពូជសាសន៍ទួលស្លែង) is a museum in Phnom Penh, the capital of Cambodia, chronicling the Cambodian genocide. The site is a former high school which was used as the notorious Security Prison 21 (S-21) by the Khmer Rouge regime from its rise to power in 1975 to its fall in 1979. Tuol Sleng (Khmer [tuəl slaeŋ]) means "Hill of the Poisonous Trees" or "Strychnine Hill". Tuol Sleng was one of at least 150 execution centers in the country, and about 20,000 prisoners were killed there.

Formerly the Chao Ponhea Yat High School, named after a royal ancestor of King Norodom Sihanouk, the five buildings of the complex were converted in August 1975, four months after the Khmer Rouge won the Cambodian Civil War, into a prison and interrogation center. The Khmer Rouge renamed the complex "Security Prison 21" (S-21) and construction began to adapt the prison to the inmates: the buildings were enclosed in electrified barbed wire, the classrooms converted into tiny prison and torture chambers, and all windows were covered with iron bars and barbed wire to prevent escapes.

From 1975 to 1979, an estimated 17,000 people were imprisoned at Tuol Sleng (some estimates suggest a number as high as 20,000, although the real number is unknown). At any one time, the prison held between 1,000–1,500 prisoners. They were repeatedly tortured and coerced into naming family members and close associates, who were in turn arrested, tortured and killed. In the early months of S-21's existence, most of the victims were from the previous Lon Nol regime and included soldiers, government officials, as well as academics, doctors, teachers, students, factory workers, monks, engineers, etc. Later, the party leadership's paranoia turned on its own ranks and purges throughout the country saw thousands of party activists and their families brought to Tuol Sleng and murdered. Those arrested included some of the highest ranking communist politicians such as Khoy Thoun, Vorn Vet and Hu Nim. Although the official reason for their arrest was "espionage", these men may have been viewed by Khmer Rouge leader Pol Pot as potential leaders of a coup against him. Prisoners' families were often brought en masse to be interrogated and later executed at the Choeung Ek extermination center.