Cortana is a fictional artificial intelligence character in the Halo video game series. Voiced by Jen Taylor, she appears in Halo: Combat Evolved and its sequels, Halo 2, Halo 3, Halo 4 and Halo 5: Guardians. She also briefly appears in the prequel Halo: Reach, as well as in several of the franchise’s novels, comics, and merchandise. During gameplay, Cortana provides backstory and tactical information to the player, who often assumes the role of Master Chief Petty Officer John-117. In the story, she is instrumental in preventing the activation of the Halo installations, which would have destroyed all sentient life in the galaxy.