Ruth Smith Lloyd (January 17, 1917 – February 5, 1995) was a 20th-century scientist whose research focused on fertility, the relationship of sex hormones to growth, and the female sex cycle. She earned a PhD in the field of anatomy from Western Reserve University in 1941, making her the first African-American woman to have reached this achievement. Lloyd worked on the faculty of medicine at Howard University from 1942 to 1977. She married physician Sterling Morrison Lloyd in 1939, and they had three children: Marilyn, Sterling and David. She died of cancer in 1995.