Cath is a fictional character from the novel series Fangirl by Rainbow Rowell. She is a college student who struggles with social anxiety and finds comfort in writing fan fiction, particularly about the fictional series Simon Snow. Cath's journey explores themes of identity, creativity, and the challenges of growing up. Throughout the story, Cath navigates her relationships with her twin sister, Wren, and her roommate, Levi. Her passion for writing and her love for the Simon Snow series serve as a backdrop for her personal growth and the development of her friendships.