Willem Johannes Maria (Pim) Levelt (born 17 May 1938 in Amsterdam) is a Dutch psycholinguist. He is a researcher of human language acquisition and speech production. He developed a comprehensive theory of the cognitive processes involved in the act of speaking, including the significance of the "mental lexicon". Levelt was the founding director of the Max Planck Institute for Psycholinguistics in Nijmegen. He also served as president of the Royal Netherlands Academy of Arts and Sciences between 2002 and 2005, of which he has been a member since 1978.