O'Hartigan
O'Hartnet
O'Hassett O'Hasset
O'Haughey O'Haffy
![O'Hennessy [Cork] coat of arms O'Hennessy [Cork] family crest](../jpg/hennessy-cork.jpg)
![O'Hennessy [Offaly] coat of arms O'Hennessy [Offaly] family crest](../jpg/hennessy.jpg)
O'Healy
O'Heffernan
O'Hegarty
O'Hennessy [Cork]
O'Hennessy [Offaly]
O'Henry
O'Herlihy O'Hurley
O'Hickey
O'Higgins
O'Hoey
O'Hogan
O'Holland
![Oiren [Lorraine] coat of arms Oiren [Lorraine] family crest](../jpg/oiren-lorraine.jpg)
O'Holligan O'Halligan
O'Hoolahan O'Holohan
O'Horan
O'Horgan O'Hargan
Oiren [Lorraine]
Oiren
![Oisy [France] coat of arms Oisy [France] family crest](../jpg/oisy2-france.jpg)
![O'Kearney O'Carney [Westmeath] coat of arms O'Kearney O'Carney [Westmeath] family crest](../jpg/fox.jpg)
Oisir
Oisy [France]
Oitelart
O'Kearney O'Carney [Westmeath]
O'Keary
O'Keaveney
O'Keeffe O'Keefe
O'Keeffe O'Keefe
O'Keegan