The Ratio Club was a small informal dining club of young psychologists, physiologists, mathematicians and engineers who met to discuss issues in cybernetics. The idea of the club arose from a symposium on animal behaviour held by the Society of Experimental Biology in Cambridge, July 1949. The club was founded by the neurologist John Bates and continued to meet until 1958.

The initial membership was W. R. Ashby, Horace Barlow, George Dawson, Thomas Gold, W. E. Hick, Donald MacKay, Turner McLardy, P. A. Merton, John Pringle, Harold Shipton, Donald Sholl, Albert Uttley, W. G. Walter and John Westcott. Alan Turing joined after the first meeting and other members included Jack Good, Philip Woodward and William Rushton.