Percy Jackson & the Olympians, often shortened to Percy Jackson or PJO, is a pentalogy of fantasy adventure novels written by American author Rick Riordan, and the first book series in the Camp Half-Blood Chronicles. Five supplementary books, along with graphic novel versions of each book in the first series have also been released. More than 69 million copies of the books have been sold in more than 35 countries.

Percy returns home for the summer vacation , where in he and his mortal mother Sally Jackson, travel to their cabin in Montauk to take their mind off things and to escape Percy's stepdad, Gabe Ugliano. However, the trip is cut short after a series of harrowing incidents, such as being attacked by the Minotaur, resulting in the death of his mother. Percy finds himself at Camp Half-Blood, a training camp for demigods like him. He discovers that he is a demigod, son of Poseidon, the Greek god of the sea. Percy also learns that his best friend, Grover Underwood, is actually a satyr, a forest spirit with a human torso, horns, and a goat’s lower body, and that Zeus is accusing Percy of having stolen his master lightning bolt, the most powerful weapon in the universe. To clear his name, save the world from another war between the Olympian gods, and maybe even save his mother, Percy sets out to retrieve the lightning bolt from Hades, who is suspected of being the real thief. Thus, Percy, Grover, and Annabeth Chase, a daughter of Athena, start on a journey to the underworld, facing numerous mythological monsters on the way. After confronting an innocent Hades, they learn that their friend Luke Castellan, son of Hermes, is the real thief who stole the bolt to allow Kronos, the defeated king of the Titans from the past, a chance to rise again.

The book was adapted into a film by Chris Columbus and 20th Century Fox, under the title Percy Jackson & the Olympians: The Lightning Thief, and was released on February 12, 2010.