Robert Alan Good NAM, NAS, AAAS (May 21, 1922 – June 13, 2003) was an American physician who performed the first successful human bone marrow transplant between persons who were not identical twins. He is regarded as a founder of modern immunology.

Among his accomplishments, in 1962, he documented the importance of the thymus gland, in 1965 he documented the important role of the tonsils in developing the immune defense systems of mammals including humans, and in 1968 he led the team that performed the first successful human bone marrow transplant between persons who were not identical twins. The patient who received the transplant was a 5-month-old boy with a profound immune deficiency that had earlier led to the deaths of eleven male members of his extended family. The boy received bone marrow transplanted from his 8-year-old sister. The transplant was successful and the boy grew up to become a healthy adult.