Sir David Cecil Smith FRS FRSE FLS (born 21 May 1930 Port Talbot, South Wales – 29 June 2018) was a British botanist. Smith was most notable for his research into the biology of symbiosis and became a leading authority on it. Smith discovered that lichens and Radiata (coelenterates) shared a similar biological mechanism in carbohydrate metabolism. Further research by Smith demonstrated similar processes in organisms that worked within a symbiotic relationship.