František Mareš (20 October 1857 – 6 February 1942) was a Czechoslovak professor of physiology and philosophy, and a nationalist politician.

During the war and after the independence of Czechoslovakia from Austria-Hungary in 1918, Mareš became active in the Czechoslovak nationalist movement.

His philosophy was briefly based upon the Vitalism of Henri Bergson and Hans Driesch.

He was a critic of positivism, reflected in his book Idealism and Realism in Natural Sciences (1903).

He also defended the Rukopis královédvorský, which were later exposed as forgeries by scientific dating methods.