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,^[1] 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.

Dr. Friesen was a recipient of the 1977 Canada Gairdner International Award^[2] "In recognition of his contributions to the understanding of the biochemistry, physiology and pathophysiology of lactogenic hormones and, in particular, for the identification of human prolactin."

His research on growth hormones in dwarf children helped in developing a therapy for the treatment of this problem. In addition his work with prolactin helped to develop the drug bromocriptine, used for the treatment of infertility.

From 1991 until 1999 he was president of the Medical Research Council of Canada and helped to transform it into the Canadian Institutes of Health Research. He was president of the National Cancer Institute of Canada and president of the Canadian Society for Clinical Investigation. He is the founding chair of Genome Canada.