According to historian C. Thomas Cairney, the O'Donovans were one of the chiefly families of the Uí Fidgenti who were a tribe of the Erainn who were the second wave of Celts to settle in Ireland between about 500 and 100 BC.

The Clans can be traced back to the descendants of the 10th century Donnubán mac Cathail (t980), son of Cahall, ruler of the Irish regional or sub-provincial kingdom of Ui-Fidgenti.

The Ui-Fidgheinte reached from Muscry Ganogh, west of Kilmallock through the plains of the Shannon, and included Adare, Askearton, Croom, Bruree and [Newcastle] Kenry.

From Donnubán mac Cathail accession to the kingship in 962 to the death of Amlaíb Ua Donnubáin in 1201, the family operated as a semi-independent to sometimes fully independent regional ruling house within the kingdom of Munster.

An ancient race in Munster, a portion of the O'Donovans became Cairbre Eva (or Uí Chairpre, see map) within the ancient regional kingdom of the Uí Fidgenti, once approximately co-extensive with the modern County Limerick,[5] and were for many centuries allies of the Eóganachta, to whom they were related by common descent from Ailill Flann Bec (or Ailill Aulom).

Although allowed to be princely in multiple ancient sources,[6] in the Irish class structure the Uí Fidgenti were only middle tier among the ruling septs of the land, as they never contested for the kingship of the greater provincial kingdom of Munster, in which they were located.

The relocation of some O'Donovans to Carbery in the later County Cork, appears to have occurred during the mid to late 13th century, primarily through their association with the MacCarthy Reagh sept.

The leading family of the Carbery O'Donovans, Clann Cathail, paid to their overlords a surprisingly small, economically insignificant rent, but the precise reason for this is lost to history.

[11] Possibly earlier times were recalled, or it may be due to the special relationship they developed with Fíngin Reanna Róin Mac Carthaig (see below).

Reverend John Begley (see references), of St. Munchin's, gives an account of the Christianization of the Norse of Limerick by the O'Donovans, and their long intermarriage.

However, the original meaning remained in usage and in the 10th century there were at least two Norse longphuirt, extensions of Limerick, which were deep in Uí Chairpre controlled territory.

[17] Up until this period the O'Donovans and O'Mahonys are generally regarded to have been allies, their ancestors Máel Muad mac Brain and Donnubán having joined forces against the Dál gCais in the 10th century.

It appears that by a fortuitous marriage to an O'Leary of Carrignacurra and the ardent support of Clan Aneslis that the branch of the celebrated Donal of the Hides were able to set aside their rivals, in the person of Diarmaid an Bhairc ("Dermot of the Bark", meaning born at sea), who were supported by Ire (Ivor) O'Donovan [Ó Donnabháin Íomhair] of the Sliocht Íomhair ("Seed of Ivor"), descendants of the legendary Ímar Ua Donnubáin, younger son of Cathal, and also by the Sliocht Tioboit ("Seed of Toby"), another distinguished sept of Clancahill.

In a terrible local conflict occurring in Rosscarbery in 1560, where Diarmaid was being inaugurated with the White Wand by the MacCarthy Reagh, Donal, with Clan Aneslis and a contingent of O'Learys, stormed the town, slaying Diarmaid and a great number of the Sliocht Íomhair at the start, and others of his followers were soon found and slaughtered in the streets of the town.

O'Donovan was a member of the General Synod of the Church of Ireland, and served as Chairman of the Standing Council of Irish Chiefs and Chieftains.

He was married to Frances Jane, daughter of the late Sir Gerald Templer, with whom his father served in the Royal Irish Fusiliers.

O'Donovan served on the Council with O'Donoghue of the Glens, McGillycuddy of the Reeks, O'Callaghan (Tortosa), Baron Inchiquin and O'Grady, the last his distant cousin.

From the ocean the territory of the O'Donovans then stretched north and northwest into the area of Drimoleague, with the well known Castle Donovan found in a valley not far from that village.

Following the Cromwellian confiscations, the infamously ungrateful Charles II of England, after first giving his deceitful word he would restore them entirely, granted the vast majority to soldiers of Cromwell's army in lieu of pay.