Ann Burden is a fictional character from the novel "Z for Zachariah" by Robert C. O'Brien. She is a teenage girl who survives a nuclear apocalypse in a remote valley, which is protected from radiation. Ann is resourceful and intelligent, using her skills to manage her daily life and maintain her safety. As the story progresses, Ann encounters another survivor, Mr. Loomis, who poses a threat to her well-being. The novel explores themes of isolation, survival, and the moral dilemmas faced in a post-apocalyptic world, highlighting Ann's resilience and determination to protect her home.