Henry J. Waternoose III, also known as Mr. Waternoose or simply Waternoose, is the hidden main antagonist of Monsters, Inc. He is the former chairman of the company, Sulley and Mike's former boss, mentor, best friend, and father figure, and Randall's former partner in crime.
After Mike explains Randall's plan to him, Waternoose agrees to help return Boo to her door; but after Mike tells him he got the wrong door, Waternoose says that he knows and that the door is for Sulley and Mike, thus revealing that he is in on Randall's plan, working for him as his loyal partner and has betrayed his former friends. Then he proceeds to push them into the door and banish them in the Himalayas. From that day on, Sulley, Mike, and Waternoose have now been enemies.
- Mr. Waternoose is constantly rumored to be the main antagonist of Monsters, Inc. and Randall's boss. This is not true as the first film has stated itself that Randall is the true mastermind and not Waternoose.
- His middle name J. is sometimes thought to stand for James. However, this is currently unconfirmed.
- Waternoose is sometimes thought to have been the founder of Monsters, Inc. However, this is false information.