O'Connor Don, An Calbhach (Charles) (1584–c.1655), head of the O'Connor Don dynasty, was eldest son of Sir Aodh O'Connor Don and his wife Mary, daughter of Brian na Murtha O'Rourke of Breifne. He was a prominent leader of the Irish nobility of Connacht during the first half of the seventeenth century. Little is known of his early life, but he spent much of this time at his castle of Knocklaghta, Co. Roscommon. Much of his relative obscurity was due to the tight grip exercised by his father over the weakening O'Connor Don dynasty. In 1613 An Calbhach emerged to contest the Irish parliamentary elections for the constituency of Roscommon, but government manipulation of the electoral proceedings resulted in his defeat at the hands of Sir John King (qv). He returned to Knocklaghta to tend to the affairs of his estates, and married (1616) Mary, daughter of Sir Theobald Burke. On the death of his father (1632), he and his family left Knocklaghta and moved to Ballintober castle, his father's seat.
It is clear, though, that he became increasingly militant during these years as a result of the anti-catholic policies of the Dublin government. Not surprisingly, this sense of grievance drove him and his son Aodh (along with most of catholic Ireland) into rebellion in late 1641. When lawless violence spread into North Connacht in November, An Calbhach and his son played prominent roles in the persecution of protestant setttlers; as organised revolt developed in December, Ballintober castle was reported to be one of the centres of rebel plotting in Connacht. Indeed, it was rumoured that the catholic nobility were planning to proclaim An Calbhach king of the province. Early in 1642, however, while Aodh was commanding the O'Connor forces in a siege of Castlecoote he was defeated and captured by a government relief force. In July, when An Calbhach assembled an army of 2,000 at Ballintober, government troops attacked and routed his forces before the walls of the castle, which withstood the subsequent attack. Aodh was released in 1643 and later served as a colonel in the confederate army, but neither he nor his father achieved prominence in the confederacy. A hint of the reason for this is perhaps to be found in An Calbhach's support for Owen Roe O'Neill (qv), in his armed opposition to the supreme council's truce with protestant forces in Munster in the autumn of 1648, and his subsequent raising of men on O'Neill's behalf: it seems unlikely that he can have fitted comfortably into the political ethos of a province in which deference to the moderating influence of the earl of Clanricarde (qv) was the norm.
By 1652 the catholic cause in Ireland was long lost, spurring Aodh to enter into articles of surrender with the protestant authorities. After a trial for murder (1653) he was found innocent of the charge levied against him. An Calbhach was not so fortunate. For his role in the plotting of the 1641 rebellion he was specifically excluded from pardon by an English statute relating to Ireland. His estates were deemed forfeit to the commonwealth and were subsequently divided among the Cromwellian soldiery. He died destitute and with a price on his head sometime between 1652 and 1655, probably in early 1655.
In 1655 his widow successfully secured 700 acres out of her husband's former estate of 7,000 acres. After his acquittal on the charge of murder, Aodh went to the Continent to serve in the forces of the exiled King Charles II. He returned to Ireland in the 1660s after the restoration but failed to obtain further employment or his father's lands prior to his death (1669). His son Aodh eventually received 1,100 acres at Ballintober in August 1677.