Jean Cashmir Felix Guyon (1831-1920) was a French urologist pathologist. He studied medicine in Paris, receiving his doctorate in 1858. He was appointed m矇decin des h繫pitaux in 1864, and was later a professor of surgical pathology (from 1877) and genitourinary surgery (from 1890) at the University of Paris. In 1878 he became a member of the Acad矇mie de M矇decine. At H繫pital Necker he held clinics that were attended by students worldwide. Although he was primarily known for work with genitourinary anatomy, Guyon is credited with the discovery of the ulnar canal at the wrist. This canal channels blood vessels and the ulnar nerve from the forearm to the hand, and is now known as Guyon's canal. Ulnar nerve compression at this location is sometimes referred to as "Guyon's tunnel syndrome".