Majestrix is a fictional title, which refers to the monarchy of the alien Shi'ar Empire featured in comic books published by Marvel Comics. The title is analogous to that of Emperor or Empress and is given to one of noble bearing who holds ultimate authority over the Empire's ruling council and provisional magistrates.
Another use of the term from the Marvel Universe is Omniversal Majestrix of Otherworld, which relates to the character of Opal Luna Saturnyne.