Rosalyn Yalow (1921–2011) was an American medical physicist and co-winner of the 1977 Nobel Prize in Physiology or Medicine for developing the radioimmunoassay (RIA) technique. Born in New York City, she faced gender discrimination throughout her career but overcame it with her determination and brilliance. Yalow's groundbreaking work in RIA revolutionized medical research, particularly in endocrinology and diabetes. She also advocated for women in science and inspired generations of scientists worldwide.