Ernest William Hornung (June 7, 1866, Middlesbrough, England - March 22, 1921, St. Jean de Luz, France) was a British author.

The third son of John Peter Hornung, a Hungarian, Ernest spent most of his life in England and France, but in 1884 left for Australia and stayed for two years where he working as a tutor at Mossgiel station.

After he returned from Australia in 1886, he married Constance Doyle, the sister of Sir Arthur Conan Doyle in 1893. Hornung published the poems Bond and Free and Wooden Crosses in The Times. The character of A J Raffles, a "gentleman thief," first appeared in The Strand and then in other British magazines during the 1890s. The stories were later published in The Amateur Cracksman (1899), a collection. Other titles in the series include The Black Mask (1901), A Thief in the Night (1905), and the full-length novel Mr. Justice Raffles (1909).

After Hornung spent time in the trenches with the troops in France, he published Notes of a Camp Follower on the Western Front in 1919, a detailed account of his time there. Other works include A Bride from the Bush (1890), The Boss of Taroomba (1894), Rogue's March: A Romance (1896), Peccavi (1900), Shadow of the Rope (1902), Denis Dent: A Novel (1904), Stingaree (1905), Fathers of Men (1912), Thousandth Woman (1913), Ballad of Ensign Joy (1917), and the collections Some Persons Unknown (1898), The Crime Doctor (1914), and Old Offenders and a Few Old Scores (1923).