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.

As of October 28, 2011, the books have been on The New York Times Best Seller list for children's book series for 245 weeks. The first book was adapted into a film titled Percy Jackson & the Olympians: The Lightning Thief in 2010, which was commercially successful, but due to major deviations from the books received mixed reviews from fans around the world. An adaptation of the second book, titled Percy Jackson: Sea of Monsters, was released in 2013.