Antoine Roquentin is the main character in the novel "Nausea" by Jean-Paul Sartre. He is a young writer living in the fictional town of Bouville, where he experiences a profound sense of existential dread and alienation. Roquentin's reflections on life lead him to question the nature of existence and his own identity. Throughout the novel, Roquentin grapples with feelings of nausea, which symbolize his discomfort with the absurdity of life. His journey explores themes of existentialism, emphasizing the struggle to find meaning in a seemingly indifferent world.