Allen Adam (Earth-Four)
- Real name: Allen Adam
- Alias: Captain Atom
- Identity: Secret
- Alignment: Good
- Universe: Earth-Four
- Gender: Male
- Hair: White
- Status Citizenship: American
- Original Publisher Charlton Comics
- First appearance: Space Adventures vol 1 #33
- Last appearance: DC Comics Presents vol 1 #90 (Feb 1986)
Allen Adam was working on an experimental rocket and he was accidentally launched into space. As he entered the upper atmosphere, the rocket exploded and Allen was atomized. However, he gained atomic abilities and was able to reform his body when he returned to the ground. Also, his hair would turn white when he transformed. He outfitted a red and yellow costume for himself and he became Captain Atom.
Later, Captain Atom would be unmasked on television. However, since his hair was white, no one recognized him. He adopted a new look and continued fighting evil. He would join the Sentinels of Justice alongside fellow heroes Blue Beetle, Nightshade, and The Question. Adam and his fellow Sentinels helped fight the Anti-Monitor and his minions during the Crisis on Infinite Earths. Following the Crisis, Adam helped Superman and Firestorm on a mission before he was erased from existence, replaced by the New Earth version of Captain Atom.