Sir Donald Bailey (15 September 1901 — 5 May 1985) was a British civil engineer who invented the Bailey bridge.

Bailey studied for a period at Sheffield University.

Bailey was a civil servant in the War Office when he designed his bridge. Another engineer, A.M. Hamilton succesfully sued Bailey for breaching a patent on Hamilton's Hamilton-Callender bridge , though the Bailey bridge was generally regarded as being superior. Bailey was knighted in 1946 for his bridge design. He died in Bournemouth in 1985.