Sir Cyril Astley Clarke (22 August 1907 – 21 November 2000) was a British physician, geneticist and lepidopterist.

In 1963 he was appointed Director of the Nuffield Unit of Medical Genetics based at the University of Liverpool and two years later was made Professor of Medicine.

In retirement he served as President of the Royal College of Physicians (1972–1977)[3] Clarke helped to develop the technique of giving Rh-negative women inter-muscular injections of anti-RhD antibodies during pregnancy to prevent Rh disease in their newborn babies.

Clarke answered an advert in the Bulletin of the Amateur Entomologists’ Society for swallowtail butterfly pupae that had been placed by Philip Sheppard.

Clarke continued research in his retirement and in 1988 he rediscovered a scarlet tiger moth colony on the Wirral Way, West Kirby, that had been started in 1961 by Philip Sheppard.