Stara Gradiška was a concentration and extermination camp in the Independent State of Croatia (NDH) during World War II.

It was established by the Ustaše regime in 1941 at the Stara Gradiška prison near the eponymous village[2] as the fifth subcamp of the Jasenovac concentration camp.

Gas experiments were conducted initially at veterinary stables near the "Economy" unit, where horses and then humans were poisoned using sulphur dioxide and later Zyklon B. Gassing was also tested on children in the yard, where the camp commandant, Ustaša sergeant Ante Vrban, viewed its effects.

Most gassing deaths occurred in the attics of "the infamous tower", where several thousand children from the Kozara region were killed in May, and 2000 more in June 1942.

[9]According to witness Milka Zabičić, the gassing stopped due to a scheduled visit by a Red Cross delegation in 1943, which did not arrive until June 1944.

Gas-vans were constructed to kill Serb and Jewish women and children who came to Stara Gradiška from the Đakovo camp in June–July 1942.

A witness, Dragutin Roller, who was a camp inmate, stated that guard Dinko Šakić "directed his guards to pack women and children into the vans, fitted a rubber hose from the exhaust to the interior and drove around and around the camp until the passengers were dead" and that "they killed at least half the group like this as soon as they arrived".

Immediately after lunch, they thrust us into the dungeon and locked us in.The most infamous staff included Nikola Gagro, Ante Vrban, Maja Buzdon, Jozo Stojčić and, notably, the commander, a Franciscan friar/military chaplain, Miroslav Filipović-Majstorović, who killed scores of women and children with his bare hands.

[11] In early April 1945, when the Partisans were fighting nearby Stara Gradiška, the Ustaše began clearing the camp, killing some of the inmates and transporting others to Lepoglava and from there to Jasenovac, where they were to be exterminated.