Henry George Friesen CC OM FRSC (born July 31, 1934) is a Canadian endocrinologist, a distinguished professor emeritus of the University of Manitoba and the discoverer of human prolactin, a hormone which stimulates lactation in mammary glands. Born in Morden, Manitoba, he obtained a Bachelor of Science in medicine and a medical degree from the University of Manitoba in 1958. From 1965 to 1973 he was at McGill University and from 1973 to 1992 he was a professor and head of the department of physiology and professor of medicine at the University of Manitoba.