Fatjohn can refer to:
- Fatjohn Orange, a character from the Fatjohn Adventures franchise. Also, a character played by John Orange in the 1990s series Fatjohn
- John Orange, an actor and singer known for playing the title character in Fatjohn; he earned the nickname "Fatjohn" because of the show.
- Fatjohn (fighter), an Orangecat character in The Mixup.
- Fatjohn (TV series), a 1990s television show starring John Orange
- Fatjohn Dollouve, a Dragoonasag war general best known for his victories at the Battle of Authonome and the Battle of the Peregos, both of which were fought over land ownership.
- Fatjohn Adventures, a series of movies originally to be based on the TV show Fatjohn.