There were originally 2 families of the name in Cork. The Ui Laoghaire of Dun Cruadha (now Castletownroche) were ousted by the Normans and are not heard of again. The second family originally inhabited the rocky sea-coast of south-west Cork, between Roscarbery and Glandore, and according to the traditional genealogies, shared their ancestry with the O? Driscolls. It appears that the coming of the Normans displaced them also; at any rate , they migrated to the mountains of Iveleary, which now incorporates their name, where they were and are particularly associated with the district of Inchigeelagh. The last Chief of the family died in Millstreet, Co. Cork in 1783; like many of the dispossessed native Irish leaders, he had upheld the old traditions of hospitality and patronage and received the deference and respect of the people in return.
One of the most famous poems in Irish literature is Caoineadh Airt Ui Laoghaire, the "Lament for Art O?Leary", a passionate outpouring of grief and anger written by his widow, Eibhlin Dubh Ni Chonaill, after his death at the hands of Abraham Morris, a member of the local Protestant gentry. Eibhlin Dubh Ni Chonaill was an aunt of Daniel O?Connell.
There has been an almost total resumption of the "O" prefix. Whereas 25% were recorded as "O?Leary" in 1890, by 1996 the figure was over 99%.
John O?Leary (1830-1907) was a member of the Fenians and in his later life became a symbol of the continuity of the nationalist cause. Yeats used his name in "Romantic Ireland?s dead and gone/It?s with O?Leary in the grave."
an t-Athair Peadar O Laoghaire (1839-1920) was active in the Gaelic League and, seeing the need for popular reading matter in Irish, produced it. Two of his works Seadna (1894-7) and Mo Sceal Fein (1915) are familiar to anyone who was educated in Ireland between 1930 and 1980..
Liam O?Leary I1910-1992) single-handedly preserved Ireland?s cinematic heritage. The Liam O?Leary Film Archive is now in the National Library of Ireland.
Dave O?Leary (1958 - ) was a stalwart of the Arsenal defence for almost 20 years and played 67 times for the Irish soccer team, scoring the winning penalty against Romania in the 1990 World Cup.