Prof John McDougal Russell Greig CBE FRSE (September 1889-1 May 1963) was a Scottish veterinarian who was Director of the Moredun Research Institute from 1930 to 1954.
He is noted for the development of several important animal vaccines: Enzootic abortion in ewes; Braxy and Louping ill.
His work on milk effectively created "clean milk" for the first time in Britain.