Alan Gregg (1890–1957) was an American physician and the Scientific Director of the Rockefeller Foundation. He played a significant role in shaping medical research and public health initiatives during the mid-20th century. Gregg oversaw the foundation's funding of medical research projects, including supporting the work of scientists such as Jonas Salk on a polio vaccine. His dedication to advancing science and improving global health had a lasting impact on the field of medicine.