Annabeth Chase is one of Percy Jackson's closest friends and girlfriend first appearing as a twelve–year-old who helps nurse him back to health after he fights the Minotaur. She is the daughter of the goddess Athena and mortal history professor Frederick Chase, from whom she has an extensive paternal family, including two half-brothers named Matthew and Bobby Chase, an uncle named Randolph, an aunt, and three cousins, one of whom, Magnus, stars in his own series, Magnus Chase and the Gods of Asgard. Annabeth has blond hair, stormy gray eyes, and tan skin . As a daughter of Athena, she is naturally intelligent, with a particular gift for strategy. She repeatedly expresses a desire to become an architect, and, at the end of The Last Olympian, she is assigned to redesign the damaged city on Mount Olympus. Her fatal flaw is hubris, and her greatest desire is to "rebuild the world from scratch". She is also described by her teacher Chiron as "territorial about her friends", which is manifested in several moments of jealousy and distrust towards other characters; in particular, toward friends of Percy. In The Lightning Thief, it is revealed that she is terrified of spiders.

Her main weapon is a short celestial bronze knife given to her by Luke Castellan, her old friend (whom she loses twice, once as he takes on the Titan Kronos' spirit, and again in The Last Olympian, as he dies). However, it breaks in the House of Hades, so now she uses a sword given to her by the giant Damasen. Annabeth also uses a Yankees baseball cap (given to her by her mother for her 12th birthday) that makes its wearer invisible, and a bronze shield (made by Charles Beckendorf) that shows any location under the sun and can be disguised as a platter. At the end of The Battle of the Labyrinth, Daedalus gives Annabeth his computer of projects that leads her to many great discoveries.[4]

Annabeth runs away from her father and stepfamily at age seven and encounters two other demigods, Luke Castellan, son of Hermes, and Thalia Grace, daughter of Zeus. They live as runaways until they are found by Grover Underwood, a satyr who has been ordered to escort Thalia back to camp. Annabeth and Percy Jackson grow close during several quests together—although she remains attached to Luke and convinced of his goodness, causing some jealousy and conflict with Percy.[5] Her attempts to bring Luke back into the fold are an important theme in the books.

Annabeth is crucial in the series. Percy undertakes a quest in The Titan's Curse to save her from Atlas's curse. Being a lifelong fan of Daedalus, Annabeth is selected the leader for the party in search of Daedalus in The Battle of the Labyrinth. The realization that he is doing more harm than good to Annabeth is what causes Luke to sacrifice himself to defeat Kronos in The Last Olympian, thereby ending the Second Titanomachy, after which Annabeth begins dating Percy. In The Son of Neptune, Percy loses virtually all of his memories except for Annabeth's name and face, thus anchoring his resolve that he does not belong in Camp Jupiter. During The Mark of Athena, Annabeth is given the task of restoring the long-lostAthena Parthenos to the Greeks by following the Mark of Athena, an ancient coin with the Athenian motto on it and special powers.[6] She also spends some time in Tartarus with Percy and Bob the Titan during the House of Hades. At the end of the series, she and Percy plan to finish high school in New York and then attend college in New Rome.

Annabeth's appearances in the crossover shorts with The Kane Chronicles and the Magnus Chase and the Gods of Asgard series make her the only character who has appeared in all three of the Greek-Roman, Egyptian, and Norse mythology series. She acts as one of the main characters in the former series, while in the latter, she serves as a supporting character who is reunited with her estranged cousin, Magnus, who is secretly a son of a Norse god, Frey.

In the film adaptations, she is portrayed by Alexandra Daddario.