Captain Universe is a character appearing in American comic books published by Marvel Comics. Created by Bill Mantlo and Michael Golden, the character first appeared in Micronauts #8. Captain Universe is the guardian and protector of Eternity. Rather than a character with a single identity, it is a persona that has merged with several hosts during its publication history.

The Micronauts are comic books featuring a group of characters based on the Mego Micronauts toy line. The first title was published by American company Marvel Comics in 1979, with both original characters and characters based on the toys. Marvel published two Micronauts series, mostly written by Bill Mantlo, until 1986, well after the toy line was cancelled in 1980. In the 2000s, Image Comics and Devil's Due Publishing each briefly published their own Micronauts series. Byron Preiss Visual Publications also published three paperback novels based on the Micronauts. In 2016, IDW Publishing published a new comic book series. A live-action film version of the Micronauts was in development by Hasbro Studios and Paramount in 2015. In May 2023, Marvel re-acquired the licensing rights to publish The Micronauts.