John Douglass Ferry (May 4, 1912 – October 18, 2002) was a Canadian-born American chemist and biochemist noted for development of surgical products from blood plasma and for studies of the chemistry of large molecules. Along with Williams and Landel, Ferry co-authored the work on time-temperature superposition in which the now famous WLF equation first appeared. The National Academy of Sciences called Ferry "a towering figure in polymer science". The University of Wisconsin said that he was "undoubtedly the most widely recognized research pioneer in the study of motional dynamics in macromolecular systems by viscoelastic techniques".