Sir Gavin Rylands de Beer FRS (1899–1972) was a British evolutionary embryologist. He was Director of the London Natural History Museum, President of the Linnean Society, and received the Royal Society's Darwin Medal for his studies on evolution.
In the First World War he served in the Grenadier Guards. Later, he taught at Oxford University zoology department. In 1938, he was made Reader in Embryology at University College London. During the Second World War de Beer again served with the Grenadier Guards reaching the rank of temporary lieutenant colonel. He worked in military intelligence, propaganda and psychological warfare. Also during the war, in 1940, he was elected Fellow of the Royal Society.
In 1945, de Beer became Professor of Zoology and was, from 1946 to 1949, President of the Linnean Society. Then he was Director of the British Museum (Natural History) from 1950 until his retirement in 1960. He was knighted in 1954, and awarded the Darwin Medal of the Royal Society in 1957.
de Beer wrote 25 books, of which these are still noteworthy: