Dowling One Name Study

John O'Hart

John O'Hart

John O'Hart (1824–1902) was an Irish genealogist. He was born in Crossmolina, Co. Mayo, Ireland.

A committed Roman Catholic, O'Hart originally planned to become a Catholic priest but instead spent 2 years as a police officer. He was an Associate in Arts at the Queen's University of Belfast. He worked at the Commissioners of National Education during the years of the Great Irish Famine. He worked as a genealogist and took an interest in Irish history. He was an Irish nationalist. He died in 1902 in Clontarf near Dublin, at the age of 78.

O'Hart's 800-page The Irish and Anglo-Irish landed gentry (Dublin 1884) was reprinted in 1969, with an introduction by Edward MacLysaght, the first Chief Herald of Ireland. Another work, Irish pedigrees; or, The origin and stem of the Irish nation, first published in 1876, has come out in several subsequent editions.

To complete his genealogies he used the writings of Cú Choigcríche Ó Cléirigh, Dubhaltach Mac Fhirbhisigh and O'Farrell, along with the Annals of the Four Masters, for the medieval pedigrees. He used the works of Bernard Burke, John Collins and others to extend his genealogies past the 17th century.

In his Irish Pedigrees, O'Hart presents the legendary origins of the Irish people, from the Biblical Adam and Eve through the kings of ancient Ireland. Irish tradition holds that every Irish person is descended from the king Milesius who emigrated from Spain in approximately 1700 BC, according to the Annals of the Four Masters. O'Hart started each of his genealogies with Adam recording Milesius as his 36th descendant.


According to O'Hart's account, Milesius had four sons, Heber, Ir, Heremon, and Amergin, who were involved, along with their uncle Ithe, in the invasion of ancient Ireland; Milesius, himself, had died during the planning. Because Amergin died during the invasion, he died without issue. It is from the four other invaders--Heber, Ir, Heremon, and Ithe—that the Irish are alleged to descend. These, according to O'Hart, are the four lines from which all true Irish descend. Conn of the Hundred Battles was a descendant of Erimon, and Brian Boru was descended from both Heber and Conn.