Edward O. Challis was a British dairy expert who became a certified member of the British Dairy Farmers Association, London, in November 1891. From 1892 to 1893 he was assistant dairy instructor to the Hampshire county council dairy school, and chief instructor from 1894. In April 1896 he was appointed as the first dairy expert in the Natal Department of Agriculture. His appointment was renewed in April 1899, and he received a fixed appointment in April 1901. During the next few years he wrote four short papers for the Natal Agricultural Journal, on the construction of small dairies (1898), grading of dairy cattle (1903), treatment of milk and cream (1904), and the transport of milk (1906).
In November 1907 Challis was appointed dairy expert in the Department of Agriculture of the Cape Colony, and from January 1911 served as superintendent of dairying in the new Department of Agriculture of the Union of South Africa - a post he still held in 1915. At that time he undertook a tour through Australia and New Zealand. His Report of a tour through the dominions of Australia and New Zealand was published by the Department of Agriculture (Pretoria, 1915). In 1919 he and other dairy inspectors were appointed as inspectors of factories for the government.