Dick Herman Jacobus de Jongh (born 19 October 1939, Enschede)[1] is a Dutch logician and mathematician and a retired professor at the University of Amsterdam.He received his PhD degree in 1968 from the University of Wisconsin–Madison under supervision of Stephen Kleene with a dissertation titled Investigations on the Intuitionistic Propositional Calculus.[2] De Jongh is mostly known for his work on proof theory, provability logic and intuitionistic logic. De Jongh is a member of the group collectively publishing under the pseudonym L. T. F. Gamut.[3] In 2004, on the occasion of his retirement, the Institute for Logic, Language and Computation at the University of Amsterdam published a festschrift in his honor.[4]