Murray Llewellyn Barr was born on June 20, 1908, in Belmont, Ontario.

He was a Canadian physician, medical researcher, and anatomist renowned for his co-discovery of sex chromatin, now known as the Barr body. This discovery was a cornerstone of human cytogenetics and led to major advancements in diagnosing genetic disorders. He studied at the University of Western Ontario (B.A, 1930; M.D., 1933; M.Sc.,1938). From 1939 to 1945, he was an RCAF wing commander. From 1936 to 1977, he served as a faculty member at the University of Western Ontario. He was also a member of the American Association for Anatomy and was nominated for the Nobel Prize in Physiology or Medicine. In 1968, he was made an Officer of the Order of Canada. In 1959, Barr received the Royal Society of Canada's Flavelle Medal. In 1962, he won the Joseph P. Kennedy Jr. Foundation Award for his contributions to understanding the causes of mental retardation. In 1963, he received the Gairdner Foundation International Award, and in 1972, he was elected a Fellow of the Royal Society of London. In 1998, he was posthumously inducted into the Canadian Medical Hall of Fame.

In 1934, he married Ruth Vivian King (1908–1995). He died on May 4, 1995, in London, Ontario.