1990 was a year in the 20th century.
- Sunday, April 22: Mother Nature fell ill due to the state of the environment, and was taken to the St. Terra Hospital for recovery. Emmett Brown arrived to show Doogie Howser and several other doctors, in great detail the condition of the world, as well as leaving information on how to help Mother Nature.
- Tuesday, May 1: Doc Brown traveled to Orlando, Florida to visit Universal Studios Florida. He was able to have an experience beyond that of usual theme park visitors, as he was able to actively participate in the rides.
Behind the scenes
- Date Unknown: Movie Licensing Games releases Back to the Future: The Board Game.
- Date Unknown: The Back to the Future: The Official Book of the Complete Movie Trilogy and Back to the Future Annual were released, though the later was only sold in the United Kingdom.
- Date Unknown: The Back to the Future Fan Club magazine 1 is published.
- Date Unknown: The Back to the Future Fan Club magazine 2 is published.
- Date Unknown: The Back to the Future Fan Club magazine 3 is published.
- Date Unknown: The Back to the Future Fan Club magazine 4 is published.
- Sunday, April 22: The Earth Day Special (which featured an appearance by Christopher Lloyd as Emmett L. Brown) aired on this day.
- Wednesday, July 18: The French-language version of Back to the Future Part III was released as Retour vers le futur 3.
- Saturday, December 15: Back to the Future released on VHS.
- Monday, December 31: The game Back to the Future Part II & III was released for the NES.