Modernism and avant-garde movements shook up literature in the late 19th and early 20th centuries. They rejected traditional forms, embraced experimentation, and sought to capture the fragmented nature of modern life and consciousness. Key figures like T.S. Eliot, Virginia Woolf, and James Joyce pioneered new techniques such as stream of consciousness and non-linear narratives. Their works challenged conventional notions of art and paved the way for future literary innovations.