Esther Greenwood is the protagonist of the novel "The Bell Jar," written by Sylvia Plath. She is a young woman in the 1950s who struggles with her identity and mental health. The story follows her experiences as she navigates societal expectations and her own aspirations, ultimately leading to a deep depression. Throughout the novel, Esther grapples with the pressures of being a successful writer and the limitations placed on women during that era. Her journey reflects the challenges of finding one's voice and the impact of mental illness, making her a complex and relatable character in American literature.