Zeus: Lord of the sky and king of Olympus. Powerful, proud, and quick to blast anyone who defies him with a master bolt. Poseidon: God of the sea and Percy’s dad. He is generally laid-back like the beach, but fiercely destructive when angered. Hades: Grim lord of the Underworld. Bitter about being excluded from Olympus, he rules the dead with cold efficiency. Hera: Queen of the gods and goddess of family. She values perfection and hates demigods born from her husband's affairs. Demeter: Goddess of agriculture and the harvest. She loves cereal and is constantly telling people to eat more whole grains. Athena: Goddess of wisdom and battle strategy. Annabeth's mother, she values intellect and is highly protective of her children. Artemis: Goddess of the hunt and moon. She leads the Hunters of Artemis, stays eternally young, and distrusts most men. Aphrodite: Goddess of love and beauty. She changes her appearance to match your ideal view of beauty and loves gossip. Hestia: Goddess of the hearth. Gentle and humble, she gave up her throne for Dionysus and watches the home fire. Ares: The hot-tempered god of war. He loves conflict, rides a Harley, and instantly clashes with Percy from day one. Apollo: God of music, poetry, and the sun. Flamboyant and arrogant, he loves driving his sun chariot and writing terrible haikus. Hephaestus: The bitter, hard-working god of fire and forges. He prefers working with machines and automatons over people. Hermes: The messenger god, full of energy and charm. He carries the caduceus and feels deep guilt over his rogue son, Luke. Dionysus: Camp Half-Blood's grumpy director, "Mr. D." Punished by Zeus, he is banned from wine and hates remembering demigod names.

Percy Jackson: Son of Poseidon. The fiercely loyal, sarcastic hero of the Great Prophecy who can control water and storms. Annabeth Chase: Daughter of Athena. A brilliant architect and strategist who relies on her intellect, knife, and invisibility cap. Grover Underwood: A loyal satyr and Percy’s best friend. He is a Protector who searches for demigods and later becomes a Lord of the Wild, dedicated to finding the lost god Pan and protecting nature.

Chiron: The wise centaur and legendary trainer of heroes (including Achilles and Hercules). At Camp Half-Blood, he acts as the activities director, using the alias "Mr. Brunner" and a magical wheelchair to disguise his horse half from mortals.