Mark Twain significantly contributed to the Realism literary movement in American literature, known for his keen observations of American life and society. His works like "The Adventures of Huckleberry Finn" highlight the complexities of race, morality, and the human experience. Twain's regional storytelling style, combined with humor and social criticism, introduced readers to authentic American voices and perspectives. His innovation paved the way for future writers, enabling them to explore social themes and the intricacies of human relationships. Twain's literary legacy remains influential in shaping American literature and its evolving landscape.