John Ellman (17 October 1753 – 22 November 1832) was an English farmer and stock breeder who developed the Southdown breed of sheep.
He inherited the tenancy to the farm with his father's death in 1780, and devoted the largest part of his time and land to rearing the local Southdown breed, changing it from a tall, lean sheep into a more squat and compact one which gave excellent mutton yield while retaining a good fleece.
His work would eventually be continued by Jonas Webb of Cambridgeshire to produce the modern form of the breed.
He was well connected, with several peers regularly corresponding with him for the advice on farming which he would give freely, was introduced to George III, and sold two of his rams to Emperor Paul I of Russia for 300 guineas.
He took great interest in local affairs as a commissioner of taxes and expenditor of Lewes and Laughton Levels, and played a role in the improvement of navigation on the River Ouse and in the redevelopment of Newhaven Harbour.