Francis Willughby (sometimes spelt Willoughby, Latin: Franciscus Willughbeius) FRS (22 November 1635 – 3 July 1672) was an English ornithologist, ichthyologist, mathematician and an early student of linguistics and games.
Willughby, Ray, and others such as John Wilkins were advocates of a new way of studying science, relying on observation and classification, rather than the received authority of Aristotle and the Bible. To this end, Willughby, Ray and their friends undertook a number of journeys to gather information and specimens, initially in England and Wales, but culminating in an extensive tour of continental Europe, visiting museums, libraries and private collections as well as studying local animals and plants. After their continental tour, he and Ray lived and worked mainly at Middleton Hall. Willughby married Emma Barnard in 1668 and the couple had three children.