Sir Geoffrey Langdon Keynes (25 March 1887 -5 July 1982) was a British surgeon and author.
He began his career as a physician in World War I, before practicing at St Bartholomew's Hospital in London, where he made notable innovations in the fields of blood transfusion and breast cancer surgery.
Keynes was also a publishing scholar and bibliographer of English literature and English medical history, focusing primarily on William Blake and William Harvey.
Dr. Keynes was married Margaret Elizabeth Darwin, the granddaughter of Charles Darwin. His older brother was the prominent economist John Maynard Keynes.