Captain Rex is a fictional character in the Star Wars franchise created by George Lucas. He was introduced as a main character in the animated The Clone Wars 2008 film and the related television series of the same name. Rex is a clone trooper of the Grand Army of the Republic, cloned from the Mandalorian bounty hunter Jango Fett, and serves the Galactic Republic under the command of Jedi General Anakin Skywalker and Jedi Commander Ahsoka Tano. Since his introduction in The Clone Wars, he has also appeared in the 2014 Star Wars Rebels television series, the 2021 Star Wars: The Bad Batch television series, the 2022 Tales of the Jedi television series and various spin-off media. Like all clone troopers in The Clone Wars, Rebels, The Bad Batch and Tales of the Jedi, Rex is voiced by Dee Bradley Baker. In Ahsoka, Rex made his live-action debut in the episode "Part Five: Shadow Warrior", voiced by Temuera Morrison in sequences set during the Clone Wars.

Star Wars: The Clone Wars is a 2008 American animated epic space opera film directed by Dave Filoni, produced by Lucasfilm Ltd. and Lucasfilm Animation, and distributed by Warner Bros. Pictures, becoming the first Star Wars film to not be distributed by 20th Century Fox. It is the first fully animated film in the Star Wars franchise and takes place shortly after Episode II – Attack of the Clones (2002), at the start of the titular Clone Wars. In the film, Count Dooku and Jabba the Hutt's uncle Ziro orchestrate a plan to turn Jabba against the Galactic Republic by framing the Jedi for the kidnapping of his son. While Anakin Skywalker and his newly assigned apprentice Ahsoka Tano attempt to deliver the child back to his father, Obi-Wan Kenobi and Padmé Amidala lead separate investigations to uncover Dooku and Ziro's plot.