Watch Your Mouth is a novel by American writer Daniel Handler.

[1] It tells the story of protagonist Joseph's lust-filled college summer spent with his Jewish girlfriend Cynthia Glass in her hometown of Pittsburgh, Pennsylvania.

The first part of the novel is laid out as an opera, with act and scene numbers as chapter titles and each of the characters being assigned a singing voice.

Joseph quickly begins to suspect that Cynthia's entire family is engaging in incestuous behaviour, and that her mother Mimi is building a golem in the basement.

The first part of the novel ends (operatically) in death.