Australian fiction author Joan O'Hagan (1926−2014) was a published author of crime fiction.

She grew up in Canberra and studied Classics at Victoria University of Wellington, New Zealand. After spending her early years in New Caledonia and England, she lived most of her life in Italy before returning to Australia in 1997. Her first job was in Noumea, New Caledonia, where she assisted in translating from the French John Grant's Journal: A Convict's Story 1803−11 for the South Pacific Commission. It was here that she met and later married Jim O'Hagan, a New Zealander from Te Kuiti.

After living in London in the early fifties, she moved to Rome with her husband where she worked in the Australian Department of Immigration. Rome remained her home for the next thirty years, during which time their daughter was born. She published five novels, two of which were translated into Italian, Swedish and Japanese. She and her husband returned to Australia in 1997.

She spent the remainder of her time in Sydney, refining her last novel about St Jerome while writing and illustrating stories for her grandsons, Isaac and Dominic.