Sophie Hatter is the main character in the novel "Howl's Moving Castle" by Diana Wynne Jones. She is a young woman who works in her family's hat shop and is known for her practical and responsible nature. After a chance encounter with the Witch of the Waste, Sophie is cursed and transformed into an elderly woman, which leads her on an unexpected journey. Throughout her adventures, Sophie discovers her own strength and resourcefulness. She eventually becomes involved with the wizard Howl and his magical moving castle. As she navigates challenges, Sophie learns about love, courage, and the importance of being true to oneself.