The yellow jack is a species of offshore marine fish in the jack family.
Yellow Jack or Yellow Jack fever may also refer to:
- Yellow fever, an acute viral disease.
- Typhoid fever, a bacterial disease.
- Yellow Jack (play), a 1934 American play about the search for the causes and treatment of yellow fever.
- Yellow Jack, a 1938 film adaptation of the play.
- The Yellow Jack, a yellow flag used to identify ships quarantined due to the presence of a disease.