Claude R. LeBrun (born 1956) is an American mathematician who holds the position of Distinguished Professor of Mathematics at Stony Brook University.

[1] That same year, he then accepted his first faculty position at Stony Brook.

In particular, he produced examples showing that the converse of the Hitchin–Thorpe inequality does not hold: there exist infinitely many four-dimensional compact smooth simply connected manifolds that obey the inequality but do not admit Einstein metrics.

LeBrun was an invited speaker at the 1994 International Congress of Mathematicians.

[7] In 2020, he was appointed as Distinguished Professor at the State University of New York.