Rachel Watson is a fictional character from the novel "The Girl on the Train" by Paula Hawkins. She is depicted as a troubled woman who struggles with alcoholism and the aftermath of her divorce. Rachel often rides the train to London, where she becomes obsessed with the lives of a couple she observes from the window. Throughout the story, Rachel's perspective and memories play a crucial role in the unfolding mystery. Her character grapples with themes of loss, identity, and the search for truth, making her a complex figure in the narrative. The novel explores her journey as she seeks to piece together the events surrounding a crime.