Anna Friederike Mathilde Klein (née Plaubel, born 1900, sometimes referred to as Anna Klein-Plaubel, date of death unknown) was a Nazi German concentration camp guard and chief warden at the Ravensbrück concentration camp.
In August 1943, she was promoted to the highest rank of Chef Oberaufseherin (Chief senior supervisor), with control and the responsibility of monitoring all of Ravensbrück camp, including slave labor, medical experiments, and death of inmates, the majority of whom were female political prisoners.
Klein reached the highest rank that the Nazis allowed a woman in a camp; she received a higher salary, better housing, better food (which was not cooked by detainees, but by other Schutzstaffel (SS) women), the best clothes, more power, and this hierarchical title of honour.
She oversaw all guards at Ravensbrück until the SS assigned her to the Sachsenhausen concentration camp in September 1944.
For the period of August 1943 to August 1944 in Ravensbrück, Klein was charged with mistreatment of inmates and participation in the selection of inmates for the gas chamber in the seventh Ravensbrück Trial in Hamburg.