Ernest Denis (January 3, 1849 – January 4, 1921) was a French historian. Denis became known as a specialist of Germany and Bohemia, and played a major role in the establishment of the Czechoslovak state in 1918. Along with Louis Léger, he is considered to be one of the most highly regarded twentieth-century historians of the Slav world in France. Upon his death, the Czechoslovak state bought his residence in Paris in order to create an institute for Slavic studies.