Lady Brett Ashley is a central character in Ernest Hemingway's novel 'The Sun Also Rises,' representing the post-war disillusionment and the complexities of modern relationships. As a strong, independent woman navigating her sexuality and emotional connections, she embodies the themes of love, loss, and the search for identity in a world marked by chaos and uncertainty. Brett's relationships with male characters highlight the gender dynamics and societal expectations of the 1920s, making her a symbol of the Lost Generation.