Everhardus Jacobus Ariëns (29 January 1918 &ndash;  3 March 2002) was a Dutch pharmacologist and professor at the Catholic University of Nijmegen (now Radboud University Nijmegen). He made important contributions to the function of receptors and the mathematical description of ligand–receptor interactions (receptor theory). Moreover, Everhardus Ariëns was a pioneer of the consideration of stereochemistry in drug development, such as the development of enantiopure drugs.