Sir Arnold Hughes "Hugh" Ennor CBE (10 October 1912 – 14 October 1977) was a senior Australian public servant and policymaker.

Ennor was born in Melbourne, the son of a joiner.^[2] For schooling, he attended a local Catholic school, O'Neill College in Elsternwick, Victoria and later Melbourne Technical College.^[1] He graduated from the University of Melbourne as a Bachelor of Science with first class honours in 1938, achieving a Master of Science in 1939 and a Doctor of Science in 1944 at the same university.^[2]

During the Second World War, Ennor was engaged by Australian Chemical Warfare Research in top secret trials in northern Queensland of mustard gas protective clothing and other counter-measures. He and fellow-biochemist J. W. Legge designed and oversaw the construction of a 100 cubic metre (3,500 cu ft) stainless-steel temperature-controlled gas chamber as part of these experiments.^[3]

Ennor was the first professor appointed by the new Australian National University in Canberra in 1948.^[2]

In February 1967, Ennor was appointed Secretary of the Australian Government Department of Education and Science.^[4][5] He served as secretary of the science department for over ten years, in the Department of Science (I),^[6] the Department of Science and Consumer Affairs,^[7] and the Department of Science (II).^[8]

He also served for a short period as Acting Secretary of the Department of Education when the Whitlam government split the Department of Education and Science into two.^[9]

Hugh Ennor died on 14 October 1977 in Canberra, aged 65.^[10] His death was just a week after his retirement from the Australian Public Service.^[11]

Ennor was made a Commander of the Order of the British Empire in January 1963 as a professor of biochemistry at the Australian National University.^[12] In June 1965 he was made a Knight Bachelor.^[13]

• Keen as Mustard (film), documentary about the mustard gas experiments