Julia Brystiger (née Prajs, born November 25, 1902, in Stryj – died November 9, 1975, in Warsaw) was a Polish-Jewish communist activist and member of the security apparatus in Stalinist Poland. She was also known as Julia Brystygier, Bristiger, Brustiger, Briestiger, Brystygierowa, Bristigierowa, and by her nicknames – given by the victims of torture: Luna, Bloody Luna, Daria, Ksenia, and Maria. The nickname Bloody Luna was a direct reference of her Gestapo-like methods during interrogations. Her pen name was Julia Preiss. Author of several books.