Susan Sto Helit, once referred to as Susan Death, is a fictional character in Terry Pratchett's Discworld series of fantasy novels. She is the granddaughter of Death, the Disc's Grim Reaper, and has a number of his abilities. She appears in three Discworld novels: Soul Music, Hogfather, and Thief of Time. Being both human and supernatural, Susan is frequently and reluctantly forced away from her attempts at normal life to do battle with malign supernatural forces or to take on her grandfather's job in his absence. Death tends to rely on her in his battles against the Auditors of Reality, particularly in situations where he has no power or influence. As the series progresses, she also begins to take on roles educating children, so that, as Pratchett mentions in The Art of Discworld, she has "ended up, via that unconscious evolution that dogs characters, a kind of Goth Mary Poppins".

Discworld is a comic fantasy book series written by the English author Terry Pratchett, set on the Discworld, a flat planet balanced on the backs of four elephants which in turn stand on the back of a giant turtle. The series began in 1983 with The Colour of Magic and continued until the final novel The Shepherd's Crown, which was published in 2015, following Pratchett's death. The books frequently parody or take inspiration from classic works, usually fantasy or science fiction, as well as mythology, folklore and fairy tales, and often use them for satirical parallels with cultural, political and scientific issues.