Cornelius O'Leary (30 September 1927 – 7 September 2006) was an Irish historian and political scientist. O'Leary was born in Limerick but was raised in Cork, where he attended University College Cork, gaining a first-class honours degree in history and Latin in 1949. He subsequently studied for a DPhil at Nuffield College, Oxford as the first student to be supervised by the psephologist David Butler. While researching his PhD, he worked at a number of secondary schools in London. O'Leary died on 7 September 2006 after a short illness. He is buried at Timoleague Abbey Cemetery in County Cork.