Kid Eternity is the name of several superheroes published by originally Quality Comics and then DC Comics. The character debuted in Quality Comic's Hit Comics #25 (December, 1942), written by Otto Binder and drawn by Sheldon Moldoff. In the 1980s, Kid Eternity was folded into the Shazam! series. Kid Eternity was rebooted in 1991 by Grant Morrison with a new focus and backstory, appearing sporadically since then and became associated with the Teen Titans. A new, female version debuted in JSA (vol. 2) #3, written by Jeff Lemire and illustrated by Diego Olortegui.

The first version of Kid Eternity is Christopher "Kit" Freeman, a teenager whose death in the 1940s was considered too soon due a to a supernatural mishap. The supernatural entity, Mr. Keeper, would rectify this bringing him to life as a superhero upholding good in the world while bestowing the power to summoning mythological or historical figures by saying "Eternity" and granting him ghost-like powers. Subjected to various revisions, the character, is retroactively connected as an agent of the Lords of Chaos. Following the New 52 reboot, he is instead a young coroner able to resurrect the dead. The second Kid Eternity is an unrevealed, teenage ghost girl whom happens upon Hawkman while the JSA battles the Injustice Society and helps the hero while learning of her origins. This version is alternatively an agent for the Lords of Order.

Prior to issue #25, Hit Comics had a series of rotating cover features, including Hercules, the Red Bee, Stormy Foster and Neon the Unknown. However, December 1942 saw the entire line-up of comics at Quality change their features (if not always the cover feature). Kid Eternity was brought in from the start as the new cover feature for Hit. The character may have been based on the 1941 film Here Comes Mr. Jordan, in which a prizefighter dies too soon in a plane crash and is given a new life by a celestial guide. Kid Eternity received a self-titled solo series in spring 1946. His antagonists, Her Highness and Silk were given their own strip in Hit Comics #29 through #57. By the late 1940s, however, Quality Comics was experiencing the post-war bust that most superhero comics were. In November 1949, Kid Eternity's self-titled magazine was discontinued and his lead slot in Hit Comics was given to Jeb Rivers, a riverboat captain.

In 1991, DC Comics' Vertigo line debuted a three-issue self-titled mini-series, written by Grant Morrison and illustrated by Duncan Fegredo, in which Kid Eternity must free Mr. Keeper from Hell.

Kid Eternity was originally a nameless boy (who remembered being called only "Kid" by his "Gran'pa") who was killed when a U-boat sank his grandfather's fishing boat during World War II. Due to a supernatural mix-up however, he was killed 75 years too soon. To rectify the error, the Kid is brought back to life for another 75 years with the mission of upholding good in the world. He is given the power to summon any good historical or mythological figure or animal by saying the word "Eternity" as well as to use the same word to make himself intangible and invisible. Kid Eternity is assisted on his duties by the clerk who had made the error, Mr. Keeper. He is sometimes shown summoning fictional figures, like Jean Valjean or the Three Witches. According to Jess Nevins' Encyclopedia of Golden Age Superheroes, "with the help of people like Sir Launcelot, Merlin and Hercules, [Kid Eternity] fights against crime, evil, the Germans, the super-strong Mr. Puny, Master Man (Satan's personal servant, who can summon history's greatest villains), and Dr. Pain, the master of agony".

Following DC's acquiring the character and later revived his title in the 1980s, the character was made a sibling of Captain Marvel Jr. (Freddy Freeman) with a similar background. Upon the death of their parents, both would be raised by their separate grandfathers. While Freddy lived with their paternal grandfather Jacob Freeman, Kitt is given to their maternal grandfather Daniel Troop, a merchant captain who's best friends with the ship's owner. Few years later during World War II, Kit and Daniel are attacked by a German U-bot and their ship is sunk, killing them in the process. When their bodies were washed ashore, Daniel's cause of death is blood loss but Kit's death was notably unusual due to his healthy appearance. While Daniel is let into the afterlife, the Wizard Shazam prevents Kit and alerts Mister Keeper, who learns Freddy was originally fated to be killed and Kit was to live to be over 75. Unable to be sent back to the living, Mister Keeper instead empowers him as a superhero and occasionally, he assists the Marvel Family while keeping his brotherhood a secret from Freddy, a fact he eventually learns alongside the Marvel Family.

In post-Crisis continuity, Kid Eternity is a servant of the Lords of Chaos, who manipulated him into serving them. Furthermore, the entities he summons are demons who assume the form of the figures he desires. In JSA, Kid Eternity is killed by Mordru. He later returns, but is killed by the Calculator.

In 2011, "The New 52" rebooted the DC universe. Kid Eternity is a police coroner who can resurrect the dead.