Oonagh
pronounced OU-naFrom the Irish word uan “a lamb” or may come from the Latin una meaning “one,” hence it is sometimes translated as “Unity.”
Not in Ireland's 2025 tables (fewer than three babies); last recorded in 2024.
More about OonaghIrish Names Starting with O
7 Irish names beginning with O for girls and boys, with what each one means and how to say it.
Updated October 2026
Irish girl names starting with O
Orla in Irish is Orlaith, pronounced OR-la, meaning “golden princess.”
No. 189 for girls in Ireland in 2025, with 23 baby girls.
More about OrlaOrlaith
pronounced OR-laOrlaith comes from the Irish Órlaith (older Órfhlaith), from ór “gold” and flaith “ruler, prince,” which is read as “princess” in women’s names, so “golden princess.”
No. 325 for girls in Ireland in 2025, with 12 baby girls.
More about OrlaithIrish boy names starting with O
Odhran
pronounced O-ranAll variants of odhra meaning “dark haired.” Seventeen saints have used the name and Odhran, abbot of Meath, was one of the 12 devotees who accompanied St. Columba to Iona.
No. 93 for boys in Ireland in 2025, with 63 baby boys.
More about OdhranOdran in Irish is Odhran, pronounced O-ran, meaning “dark-haired.”
Not in Ireland's 2025 tables (fewer than three babies); last recorded in 1974.
More about OdranOisin
pronounced osh-EENThe son of the legendary warrior Fionn Mac Cool and the goddess Sive. His mother was turned into a deer by the Dark Druid and she reared him in the forest until he was seven years old.
No. 5 for boys in Ireland in 2025, with 331 baby boys.
More about OisinOwen in Irish is Eoghan, pronounced O-in, meaning “born of the yew tree.”
No. 317 for boys in Ireland in 2025, with 13 baby boys.
More about OwenOf the 7 Irish names starting with O here, 3 are for girls and 4 for boys. The ones readers look up most are Oisin, Owen and Orla.
Most popular in Ireland in 2025
The O names on this page that the most babies were given in 2025, by the Central Statistics Office’s ranking (girls and boys are ranked separately).