David Andrew Day (born 24 June 1949) is an Australian historian, academic, and author.

The son of a weather forecaster with Australia's Bureau of Meteorology, Day grew up in Melbourne and Charleville, Queensland before commencing accounting studies in which he performed poorly owing to his political activity, which included protesting against Australia's involvement in the Vietnam War.^[1] After a short period of work, Day returned to his studies and graduated with first-class Honours in History and Political Science from the University of Melbourne and was awarded a PhD from the University of Cambridge.

Day has been a Junior Research Fellow at Clare College in Cambridge, founding head of History and Political Science at Bond University, official historian of the Australian Customs Service, Keith Cameron Professor of Australian History at University College Dublin, and Professor of Australian Studies at the University of Tokyo. He is currently an Honorary Associate in the History Program at La Trobe University in Melbourne.^[2]

Day has written widely on Australian history and the history of the Second World War. Among his many books are Menzies and Churchill at War and a two-volume study of Anglo-Australian relations during the Second World War. His prize-winning history of Australia, Claiming a Continent, won the prestigious non-fiction prize in the 1998 South Australian Festival Awards for Literature. An earlier book, Smugglers and Sailors, was shortlisted by the Fellowship of Australian Writers for its Book of the Year Award. John Curtin: A Life was shortlisted for the 2000 NSW Premier's Literary Awards' Douglas Stewart Prize for Non-Fiction.

• Menzies & Churchill at war: a controversial new account of the 1941 struggle for power. Sydney: Angus & Robertson. 1986. p. 271. ISBN 0-207-15169-5.
• The Great Betrayal: Britain, Australia and the Onset of the Pacific War, 1939–42. Sydney: Angus & Robertson. 1988. p. 388. ISBN 0-207-15328-0.
• Reluctant Nation: Australia and the Allied Defeat of Japan, 1942–45. Melbourne: Oxford University Press. 1992. p. 370. ISBN 0-19-553453-0.
• Brave new world: Dr. H.V. Evatt and Australian foreign policy 1941–1949. St Lucia, Queensland: University of Queensland Press. 1996. p. 182. ISBN 0-7022-2608-4.
• Claiming a Continent: A New History of Australia. Sydney: Angus & Robertson. 1996. p. 488. ISBN 0-207-19670-2.
• John Curtin: A Life. Sydney: HarperCollins. 1999. p. 610. ISBN 0-207-19669-9.
• Chifley. Sydney: HarperCollins. 2001. p. 562. ISBN 0-7322-6702-1.
• The Politics of War. Sydney: HarperCollins. 2003. p. 750. ISBN 0-7322-7333-1. Completely revised and updated edition bringing together two earlier works: The Great Betrayal and Reluctant Nation.
• Conquest: A New History of the Modern World. Sydney: HarperCollins. 2005. p. 370. ISBN 0-7322-7765-5.
• The Weather Watchers: 100 years of the Bureau of Meteorology. Carlton: Melbourne University Publishing. 2007. p. 530. ISBN 978-0-522-85275-2.
• Conquest: how societies overwhelm others. New York: Oxford University Press. 2008. pp. 288. ISBN 978-0-19-534011-2.
• Andrew Fisher: Prime Minister of Australia. London: Fourth Estate. 2008. p. 496. ISBN 978-0-7322-7610-2.
• Flaws in the ice: In search of Douglas Mawson. Melbourne: Scribe. 2013. p. 316. ISBN 978-1-9220-7074-6.
• The Story of a Prime Minister: Paul Keating, a Biography. Sydney: HarperCollins Australia. pp. 576. ISBN 978-0-7322-8425-1.
• Maurice Blackburn: Champion of the People. Melbourne: Scribe. 2019. ISBN 978-1-925713-78-7.

• Day, David; Australian Customs Service (1992). Smugglers and Sailors: The Customs History of Australia, 1788–1901. Canberra: Australian Government Publishing Service Press. p. 528. ISBN 0-644-24751-7.
• Day, David; Australian Customs Service (1996). Contraband and Controversy: The Customs History of Australia from 1901. Canberra: Australian Government Publishing Service Press. p. 558. ISBN 0-644-33151-8.

• Interview by Marshall Poe with David Day in New Books in History on 11 July 2008 – streaming audio interview
• Personal homepage of David Day
• Conquest: a review by Morag Fraser in The Age on 30 July 2005