The Ultimate Galactus Trilogy is a collection of three comic book limited series published by Marvel Comics. All three series are set in the Ultimate Marvel universe and are written by Warren Ellis. The series showcase the arrival of the planet-eating entity Gah Lak Tus on Earth.

Ultimate Marvel, later known as Ultimate Comics, was an imprint of comic books published by Marvel Comics, featuring reimagined and modernized versions of the company's superhero characters from the Ultimate Marvel Universe, later known as the Ultimate Universe. Those characters include Spider-Man, the X-Men, the Ultimates, the Fantastic Four, and others. The imprint was launched in 2000 with the publication of the series Ultimate Spider-Man and Ultimate X-Men in 2001, followed by The Ultimates and Ultimate Fantastic Four in 2002 and 2004 respectively providing new origin stories for the characters. The reality of Ultimate Marvel is designated as Earth-1610 as part of the Marvel Comics Multiverse.