Frank Rattray Lillie, American zoologist and embryologist (d. 1947)
Frank Rattray Lillie (June 27, 1870 – November 5, 1947) was an American zoologist and an early pioneer of the study of embryology. Born in Toronto, Ontario, Canada, Lillie moved to the United States in 1891 to study for a summer at the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts. Lillie formed a lifelong association with the laboratory, eventually rising to become its director in 1908. His efforts developed the MBL into a full-time institution.

Lillie was appointed an Assistant Professor at the University of Chicago in 1900. He was named Chairman of the Department of Zoology in 1910 and Dean of the Division of Biological Sciences in 1931. His research there was instrumental in the development of the field of embryology. He identified the influence of potassium on cell differentiation and elucidated the biological mechanisms behind free-martins. Lillie was instrumental in founding the Woods Hole Oceanographic Institution and served as its first president. He also served at times as the chairman of the National Academy of Sciences and the United States National Research Council.