Swedish anatomist and anthropologist best-known for his studies of the histology of the nervous system.

Retzius' Das Menschenhirn, 2 vol. (1896; “The Human Brain”) was perhaps the most important work written on the gross anatomy of the brain during the 19th century. He served as a professor of histology at the Karolinska Mediko-Kirurgiska Institutet, Stockholm (1877–1900), where he made important contributions to anatomical descriptions of the muscles of the eardrum, the bones of the middle ear, and the Eustachian tube. Retzius also made a useful study of ancient Swedish and Finnish skulls.