Charles H. Best (born February 27, 1899, West Pembroke, Maine, U.S.—died March 31, 1978, Toronto, Ontario, Canada) was a physiologist who, with Sir Frederick Banting, was one of the first to obtain (1921) a pancreatic extract of insulin in a form that controlled diabetes in dogs. The successful use of insulin in treating human patients followed. But because Best did not receive his medical degree until 1925, he did not share the Nobel Prize for Physiology or Medicine awarded to Banting and J.J.R. Macleod in 1923 for their role in the work. Best also discovered the vitamin choline and the enzyme histaminase. He was one of the first to introduce anticoagulants in treatment of thrombosis (blood clots).
In May 1921, while still an undergraduate, Best became a laboratory assistant to Banting at the University of Toronto. In the months that followed, they performed their prizewinning research on insulin. Best continued as research associate in the Banting and Best Department of Medical Research, which was created at the university in 1923, and he succeeded Banting as its director (1941–67). With Banting he wrote Internal Secretions of the Pancreas (1922).