Xavier Leroy (born 15 March 1968) is a French computer scientist and programmer. He is best known for his role as a primary developer of the OCaml system. He is Professor of software science at Collège de France. Before his appointment at Collège de France in 2018, he was senior scientist (directeur de recherche) at the French government research institution Inria. Leroy was admitted to the École normale supérieure in Paris in 1987, where he studied mathematics and computer science. From 1989 to 1992 he did his PhD in computer science under the supervision of Gérard Huet. He is an internationally recognized expert on functional programming languages and compilers. In recent years, he has taken an interest in formal methods, formal proofs and certified compilation. He is the leader of the CompCert project that develops an optimizing compiler for C (programming language), formally verified in Coq. Leroy was also the original author of LinuxThreads, the most widely used threading package