Ralph Waldo Emerson was an American essayist, lecturer, and poet who was a leading figure in the transcendentalist movement of the mid-19th century. He is best known for his essays, such as "Self-Reliance" and "Nature," which emphasized individualism, self-reliance, and the importance of connecting with nature. Emerson's work had a significant impact on American literature and philosophy, and he remains a prominent figure in the history of American thought.