David J. Farrar (3 September 1921 – 16 April 2021) was an English engineer who led the Bristol team that developed the Bristol Bloodhound surface-to-air missile, which defended Britain's nuclear deterrent for many years and was widely sold abroad. His main achievements in cost engineering were confidential until 2000. He saved two companies from bankruptcy, achieved cost reductions of over £1 million, and trained engineers in cost engineering. His methods are the basis of a major Australian product cost reduction initiative.