Irmgard Ilse Ida Grese (7 October 1923 – 13 December 1945) was a Nazi concentration camp guard at Ravensbrück and Auschwitz, and served as warden of the women's section of Bergen-Belsen. She was a volunteer member of the SS.

Grese was convicted of crimes involving the ill-treatment and murder of Jewish prisoners committed at Auschwitz and Bergen-Belsen concentration camps, and sentenced to death at the Belsen trial. Executed at 22 years of age, Grese was the youngest woman to die judicially under British law in the 20th century. Auschwitz inmates nicknamed her the "Hyena of Auschwitz" ("die Hyäne von Auschwitz").