Susan Sto Helit, usually referred to as just Susan, is a character in the Discworld books. She is the daughter of Ysabell, Death's adopted daughter, and Mort, Death's one-time apprentice; as a result she is Death's "granddaughter" and has inherited some of his abilities, sometimes filling in for him in an official capacity. She is a protagonist in a sub-series of Discworld novels, though is the primary character only in Hogfather.
The Susan sub-series comprises three novels:
Susan has appeared in two Discworld adaptations for the screen: in the animated version of Soul Music (TV), she is voiced by Debra Gillet. In the live-action telemovie Terry Pratchett's Hogfather, Susan was played by Michelle Dockery.