Percy Jackson: The protagonist, a 12-year-old boy who discovers he is the son of Poseidon, the Greek god of the sea. He's impulsive, brave, and loyal, and he struggles to control his powers while trying to clear his name of a crime he didn't commit.
Annabeth Chase: A daughter of Athena, the Greek goddess of wisdom and warfare, Annabeth is intelligent, resourceful, and a skilled strategist. She's Percy's close friend and a crucial part of his journey.
Grover Underwood: A satyr who is Percy's best friend and protector. He's nervous and clumsy but ultimately brave and loyal, determined to keep Percy safe. He's also a "tree nymph" and can control plants.
Luke Castellan: A charming and seemingly friendly son of Hermes, the messenger god. He initially appears to be a friend to Percy but later reveals himself as a villain.
Clarisse La Rue: A daughter of Ares, the god of war, and Percy's rival at Camp Half-Blood. She's fierce, competitive, and initially hostile towards Percy, but she eventually comes to respect him.
Mr. D (Dionysus): The God of Wine and revelry, Mr. D is the stern, but ultimately helpful, headmaster of Camp Half-Blood.
Chiron: The wise centaur who is the activities director at Camp Half-Blood. He's a gifted teacher and mentor to the demigods, offering Percy valuable advice and guidance.
Other Important Characters:
* Sally Jackson: Percy's loving and supportive mother, who is unaware of his true nature.
* Gabe Ugliano: Percy's abusive stepfather, whom Percy despises.
* Thalia Grace: A daughter of Zeus who is a Hunter of Artemis. She's a powerful warrior and a close friend of Annabeth.
* The Furies: Three female spirits of vengeance who are tasked with capturing Percy.
These are just some of the main characters in "The Lightning Thief." The story is filled with many other gods, demigods, and monsters that play key roles in the adventure.