Jozef A.M. K. IJsewijn (Zwijndrecht, December 30, 1932 - Louvain, November 27, 1998) was a Belgian Latinist of the Flemish language. He is known as the "father" of the study of the Neolatin (Latin from the beginning of humanism onwards, XV century onwards).

IJsewijn studied classical philology at the Catholic University of Louvain where he graduated in 1955. He then obtained a scholarship to write the doctoral thesis and obtained a doctorate in 1959. At first he devoted himself to the study of antiquity and papyrology. After being a teacher since 1962, he became a professor at the same university in Leuven from 1967 until his retirement in 1997.

The interest for the neo-Latin led IJsewijn to refound the humanistic journal Lovaniensia and give it the subtitle of Journal of Neo-Latin Studies. In 1971 he founded the International Association for Neo-Latin Studies.

His best known work is the 'Companion to neo-Latin Studies' (1977, with reissues to make two volumes). And he was also editor of numerous Renaissance texts by authors such as Erasmus of Rotterdam, Justus Lipsius, or Joan Lluis Vives.

He was a member of the Koninklijke Academie voor Wetenschappen, Letter in Schone Kunsten and was also president, "Fellow" of the British Academy and the Europaea Academy; foreign member of the Finnish Academy of Sciences, and corresponding member of the Göttinger Akademie der Wissenschaften. He received the Francqui prize (1980).