The Thinker's Library was a series of 140 small hardcover books published between 1929 and 1951 for the Rationalist Press Association by , London, a company founded by the brothers Charles and John Watts. The series was launched at the time when Watts & Co. was being run by Charles Albert Watts. A member of the company's board of directors, Archibald Robertson, took an active interest in setting up the series and it was he who suggested the series' name.