Star Wars: Original Trilogy includes the first three movies of the franchise: Star Wars, The Empire Strikes Back and Return of the Jedi. More: en.wikipedia.org.
If you were a Jedi and they invited you, would you choose the light or the dark side of the Force?
Star Wars: Sequel Trilogy
Star Wars: Prequel Trilogy
Back to the Future trilogy
The Santa Clause: Movie Trilogy
Toy Story trilogy
The Hobbit: Movie Trilogy
The Fast & Furious: Movie Series
Harry Potter: Movie Series
Grindhouse