Felix Hausdorff (November 8 1868 - January 26 1942) was a German mathematician who is considered to be one of the founders of modern topology and who contributed significantly to set theory and functional analysis. He defined and studied partially ordered sets, Hausdorff spaces, and the Hausdorff dimension. He proved the Hausdorff maximality theorem. He published philosophical and literary works under the pseudonym "Paul Mongré".

Hausdorff studied in Leipzig and taught mathematics there until 1910, when he became professor of mathematics in Bonn. When the Nazis came to power, Hausdorff, who was Jewish, felt that as a respected university professor he would be spared from persecution. However, his abstract mathematics was denounced as "Jewish", useless, and "un-German" and he lost his position in 1935. When in 1942 he could no longer avoid being sent to a concentration camp, Hausdorff committed suicide together with his wife and sister-in-law.