Annabeth Chase is the demigod daughter of Athena (the Greek goddess of wisdom and battle) and Fredrick Chase, the step-daughter of Mrs. Chase, the older half-sister of Matthew and Bobby, the cousin of Magnus and is one of the main characters in the 2005-2009 book series Percy Jackson and the Olympians and it's 2010-2014 sequel series The Heroes of Olympus.
She serves as the best friend (other than Grover Underwood), love interest and later girlfriend of Percy Jackson.
She ran away from home at age 7 and later, with help from Athena, met and befriended two other demigods a 14-year-old son of Hermes (the Greek God of Thieves) called Luke Castellan (whom Annabeth develops a crush on) and a 12-year-old daughter of Zeus (Greek God of the Sky) called Thalia Grace. Eventually the three demigods were found by a satyr named Grover Underwood, who escorted them to a demigod training camp called Camp Half-Blood, whilst being pursed by a group of monsters. When reaching the camp, Thaila sacrificed herself so Annabeth, Luke and Grover could get to safety and was turned into a pine tree by Zeus.
Five years later, Annabeth now 12 meets the camp's newest camper Percy Jackson (who is later revealed to be a son of Poseidon, the God of the Sea). In the first series, Annabeth aids Percy in fighting the Titans and their allies, including Luke (who turned against the gods after feeling unwanted by Hermes), which hurt Annabeth greatly. In the last book, The Last Olympian, Annabeth and Percy battle the Titan King Kronos (who is using Luke as a host). Annabeth is able to talk Luke back to his senses after reminding him of his promise to her when they first met about being a family. Luke destroys Kronos by stabbing his Achilles heel (his left armpit), but dies afterwards, but not before reconciling with Annabeth and Percy. Afterwards, Annabeth starts a relationship with Percy.
In the second series, taking place a few months after the previous series, Percy goes missing and Annabeth goes to look for him. It is later revealed that Hera had switched Percy with a Roman demigod named Jason Grace (a son of Jupiter) from Camp Half-Blood's Roman counterpart Camp Jupiter in order to make both camps unite to battle the Earth Goddess and mother of the Titans Gaia and her other children the Giants. Annabeth joins Percy, Jason, Piper McLean (a daughter of Aphrodite, Greek Goddess of Love), Leo Valdez (a son of Hephaestus, Greek God of Fire), Frank Zhang (a son of Mars, Roman God of War) and Hazel Levesque (a daughter of Pluto, Roman God of the Underworld) in a quest to defeat the Giants and prevent Gaia's rising. In the last book of the series The Blood of Olympus, following Gaia's defeat and the union of the camps, Annabeth and Percy decide to spend their senior year together before going to college in New Rome (a city in Camp Jupiter where demigods can live and raise their families).
In the film adaptations of the books, Annabeth is played by Alexandra Daddario. In the first film Percy Jackson and the Olympians: The Lightning Thief, Annabeth is a brunette whereas in the sequel Percy Jackson: Sea of Monsters, she is blonde (which is Annabeth's hair colour in the books).