The 501st Legion (a.k.a. Vader's Fist) is a worldwide organization of Star Wars fans, formed by Albin Johnson. The 501st Legion is the world's largest Imperial costuming organization, spanning the entire United States and 21 other countries. Its website is 501st.com. The 501st can often be found at promotional events for almost anything related to Star Wars and frequently put their "fame" to use at numerous charity events throughout the year (i.e., Toys for Tots, MDA Telethons, local children's hospitals, etc.). Thanks to their recent inclusion in the novel Survivor's Quest and the film Star Wars Episode III: Revenge of the Sith, members of the 501st Legion are the only known living Star Wars characters.

Formed initially for the pristine white Death Star armored troops, the group now includes all trooper variations as well as Sith Lords, bounty hunters and other villains from the series.

As a tribute to the loyal group, the legion of blue clone troopers in Revenge of the Sith that Darth Vader leads into Jedi Temple during the Great Jedi Purge, is designated as the 501st. Although not mentioned in the film itself, much of the support and merchandising material for the film make this reference, including the videogame Star Wars: Battlefront II.