Percy Jackson: Sea of Monsters (also known as Percy Jackson & the Olympians: The Sea of Monsters and Percy Jackson and the Sea of Monsters) is a 2013 fantasy adventure film directed by Thor Freudenthal from a screenplay by Marc Guggenheim, based on the 2006 novel The Sea of Monsters by Rick Riordan. The sequel to Percy Jackson & the Olympians: The Lightning Thief (2010), it is the second and final installment in the Percy Jackson film series.

The film continues the adventures of Percy Jackson (Logan Lerman) and his friends as they journey to the eponymous Sea of Monsters to retrieve the Golden Fleece in order to save the tree barrier that protects their home. Lerman, Brandon T. Jackson, Alexandra Daddario, and Jake Abel reprise their roles from the previous film, while Nathan Fillion and Anthony Head replace Dylan Neal and Pierce Brosnan, respectively. New additions to the cast include Leven Rambin, Douglas Smith, and Stanley Tucci.

Percy Jackson: Sea of Monsters was released theatrically in the United States on August 7, 2013, by 20th Century Fox. The film received mixed-to-negative reviews from critics, with praise for its visuals and action, but criticism for its plot and characters. It grossed $200.9 million worldwide against a production budget of $90 million. A sequel based on The Titan's Curse was planned, but never produced. Following the acquisition of 21st Century Fox by Disney in 2019, Disney consequently gained the rights to the Percy Jackson novels, upon which Riordan pitched a television adaptation that debuted on Disney+ in 2023.

Seven years before the events of the film, young Annabeth Chase, Thalia Grace, Luke Castellan and Grover Underwood were pursued by monsters on their way to Camp Half Blood. When Thalia sacrificed herself to save her friends, her father, Zeus, honored her act by turning her into a tree, which formed a protective barrier around the camp, keeping everyone inside within a safe zone.

In the present day, Percy Jackson now attends camp and has befriended Annabeth and Grover. His quest for Zeus's lightning bolt has faded in popularity and he is called a one-quest wonder by camp bully Clarisse La Rue. He is joined at camp by a young cyclops named Tyson, a previously unknown son of a sea-nymph and Poseidon, and therefore Percy's half-brother. After camp is attacked by a Colchis bull, the campers discover Thalia's tree has been poisoned by Luke and the barrier is weakening.

Annabeth learns about the healing powers of the Golden Fleece, which Grover senses is located off the coast of Florida, and they propose a quest to retrieve it to heal Thalia's tree. As it will involve crossing the Sea of Monsters (Known to humans as the Bermuda Triangle), camp counsellor Mr. D denies them, but then claims the idea as his own and selects Clarisse for the quest.

Meanwhile, Percy consults the Oracle of Delphi, who tells of a prophecy that a half-blood of one of the three elder gods will one day either save or destroy Olympus. Chiron informs him that, as he is the only living human half-blood of the eldest gods, the Prophecy may refer to him.

Percy, Annabeth, Grover and Tyson decide to leave camp in pursuit of the Fleece. They ride in the Chariot of Damnation (a New York City cab) as far as Washington D.C., where its drivers - the Graeae - eject them for lacking drachmas. Luke's cronies kidnap Grover and, with the help of Hermes, the others track him down to Luke's yacht, the Andromeda, where they are captured after boarding.