The Forgotten One (also known as Hero and Gilgamesh) is a fictional character appearing in American comic books published by Marvel Comics. He first appeared in The Eternals #13 (July 1977) and was created by Jack Kirby. He is a member of the near-immortal hidden race known as the Eternals. He has also been a member of the Avengers.

Don Lee portrayed Gilgamesh in the Marvel Cinematic Universe, debuting in Eternals (2021).

The Forgotten One was created by Jack Kirby, and first appeared in The Eternals #13 (July 1977).

During his millennia of activity, the adventurer and warrior Forgotten One has used the names of or been mistaken for numerous heroes of myth and legend, including Gilgamesh and Hercules. He became an outcast from his fellow Eternals when their ruler, Zuras, decreed that he had been too proud a meddler in the mortal world and confined him to a sector of Olympus. Eventually the Eternal known as Sprite convinced him to come out of exile and journey to the mother-ship of the Fourth Host of the Celestials to assist the Eternals in battle against the Deviants.

After this battle, he was renamed Hero by the One Above All, the chief of the alien Celestials, who had created the Eternals and Deviants. After losing a battle with Thor, Hero and the other Eternals assisted Thor in battling the host of the Celestials to prevent them from destroying humanity. Hero also fought Hercules.

Hero later became known as the Forgotten One. He helped the other Eternals in battle against Ghaur.

Later, when the membership of the Avengers had been virtually emptied, the Forgotten One joined them for a time. He renamed himself Gilgamesh, donning a costume that resembled the hide of the Bull of Heaven and went to work as a monster-slayer. He assisted the Avengers in battles against the Growing Man, Nanny and Orphan-Maker and N'astirh's demons. He participated in the Avengers' battle against Supernova and helped them fight the U-Foes. He assisted the Avengers in their struggle with the Lava Men, and was somehow severely injured during the battle. Gilgamesh was brought to the Eternals' home of Olympia, which had temporarily fallen into the Negative Zone, to recover from his injuries. There, he fought against Blastaar, who had temporarily disintegrated the other Eternals. Gilgamesh left the Avengers at that time, as his essence had been bound to Olympus. He later recovered from his injuries and defeated B'Gon the sorcerer, thereby winning a reputation as a hero on modern day Earth. Gilgamesh was later seen among the superhumans selected by Her as potential mates.

He returned to the Avengers Mansion during "The Crossing" crossover event, only to be killed by Neut, an agent of the time traveler Immortus, who was at the time disguised as Kang the Conqueror. It was later shown that Gilgamesh is alive and once again associated with his fellow Eternals. He had lost his memory because a reality change created by Sprite and was living as circus' strongman in Brazil. He was deceived by Ajak in killing Makkari and damaging the Eternals' resurrection machine. Later, he team up with Hercules and then travelled to Deviant Lemuria, where he helped Thor, who was fighting the deviants led by Ghaur.