Poseidon is Percy Jackson’s divine father in Rick Riordan’s Percy Jackson & the Olympians series.
Percy is a demigod, meaning one of his parents is a Greek god and the other is human. Poseidon, god of the sea, claims Percy in The Lightning Thief, the first novel, after Percy reaches Camp Half-Blood. This makes Percy one of the children of the “Big Three,” alongside children of Zeus and Hades.
The parentage explains several of Percy’s abilities, including his strength in water, his capacity to breathe underwater, and his connection with sea creatures. It also places him at the center of an Olympian conflict because an ancient agreement limited the Big Three’s children.
Poseidon is sometimes confused with Zeus because both are major Olympian gods. In Riordan’s series, Zeus rules the sky, Hades rules the Underworld, and Poseidon rules the sea.