Adriaan van Royen (11 November 1704 in Leiden – 28 February 1779 in Leiden) was a Dutch botanist. He was a professor at Leiden University and is associated with Carl Linnaeus.
Van Royen trained at the University of Leiden and graduated as a medical doctor in 1728 for his thesis Dissertatio botanico-medica de anatome et œconomia plantarum. He was later appointed professor of botany at the university from 1732–1755 and later professor of medicine (1755–1775).
He is best known for his work on flora of Southeast Asia. He was a colleague of George Clifford III, a wealthy Dutch merchant and governor of the Dutch East India Company living in Haarlem, and a noted source of new introductions from the East Indies and the Cape. Adriaan van Royen formed a close relationship with Linnaeus, who had visited the Leiden Botanic Garden during a stay in Leiden between 1737 and 1738.
The genus Royena L. (= Diospyros sect. Royena (L.) F.White), in the Ebenaceae, and Melastoma royenii Blume. Sutton, D.A. are named after him.