| William Hagarty O'Leary | |
| Office1: | Member of Parliament for Drogheda |
| Term1: | 1874-1880 |
| Birth Name: | William Hagarty Leary |
| Birth Place: | Dublin, Ireland |
| Death Date: | 15 February |
| Education: | Royal College of Surgeons |
| Children: | 9 |
William Hagarty O'Leary (1836 - 15 February 1880) was an Irish medical doctor and politician.
O'Leary was born in Dublin as William Hagarty Leary; he later adopted the O'Leary form of the name. He and his wife had nine children. He became a fellow of the Royal College of Surgeons in 1871. He was elected Member of Parliament for Drogheda in 1874 and sat for the seat as a Home Ruler until his death in 1880. A contemporary remarked of him that "Mr. O'Leary spoke very eloquently, though somewhat floridly. In stature he was very short." He was buried in Glasnevin Cemetery.[1]