David Day is an Australian historian and author. Day has written widely on Australian history, biographies of prime ministers, and the history of the Second World War. Day's latest work is a two-part biography of former Australian prime minister Bob Hawke, Hawke PM: The Making of a Legend and Young Hawke: The Making of a Larrikin.

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. John Curtin: A Life was shortlisted for the 2000 NSW Premier's Literary Awards' Douglas Stewart Prize for Non-Fiction. His 2013 book, Antarctica: A Biography, offers an engaging account of the frozen continent. Day’s biography of former prime minister Paul Keating was published in 2015.