Donnellan, James (1588?–1665), lawyer, was third son of Nehemias Donellan (qv), archbishop of Tuam (1595–1609), and his wife Elizabeth O'Donnell of Tyrconnell. He was a scholar of TCD in 1607, graduating BA (1610) and MA (1613). He was elected a fellow of Trinity (1612) and as such was to teach Greek and Latin. On 9 June 1612 he was presented with a rectory in Limerick as a means of supporting himself as a scholar. At the request of Sir James Ley (qv) he was admitted to Lincoln's Inn on 11 June 1616 and was called to the bar on 4 February 1623. He came to practise in Ireland, being admitted a member of King's Inns on 6 November 1623. Donnellan was appointed third justice of the court of Connacht in 1627 and became chief justice of the same on 10 March 1634. He sat for Trinity College in the 1634–5 parliament, where he acted as a government supporter. On 17 August he was made third justice of common pleas, receiving licence to continue to hold the office of chief justice of Connacht. The lord deputy, Thomas Wentworth (qv), saw the appointment as a sop to the natives, although he thought highly of Donnellan who also acted as justice of the assize, going on the north-west circuit for 1637–41. In 1639 he was elected treasurer of King's Inn. Donnellan was closely associated with the earl of Clanricard (qv), from whom he leased land in Co. Roscommon. He also had a house in Rathmire, Co Westmeath.
Donnellan was in Connacht when the 1641 rebellion began. In May 1642 he helped Clanricard keep the peace between the citizens of Galway city and the royal troops stationed there. By the summer of 1643 he was in Dublin, where he was a member of the inner circle of the marquess of Ormond (qv), committed to bringing about a cessation with the confederates. He acted as a link between Ormond and Clanricard, advising Clanricard to ask the king for a marquisate. In April 1644 he was selected to act as a delegate representing the Irish government in negotiating with the confederates before the king in Oxford. Donnellan and another delegate, Sir Gerald Lowther (qv), were expected back in Dublin in August but curiously did not return until Christmas. Suspecting Donnellan's loyalty, on 19 November 1644 Ormond removed him from common pleas. Years later Henry Cromwell (qv) would declare that Donnellan had always been faithful to parliament. This is clearly untrue, but suggests that Ormond's suspicions were well founded. Certainly his letters to Clanricard in 1642–3 show that Donnellan was aware that the king was losing the civil war.
Donnellan came back into favour under the commonwealth. In 1651 he was made a commissioner of justice for Leinster, and was sent on the circuit to Ulster on 15 April 1653. He played an active role in the repressive measures used to put down resistance to the government, hanging a number of his own countrymen. On 1 March 1655 he became justice of the assize for Ulster and Louth and was restored as justice of common pleas by Henry Cromwell on 13 July 1655. However, many in the government regarded him with suspicion due to his Irish background, and an attempt was made to revoke his promotion. Henry Cromwell defended him and it appears as if he eventually succeeded in upholding his appointment. In any case, he continued to sit on a number of commissions under the commonwealth. Following the restoration he became chief justice of common pleas on 30 November 1660. Made a privy counsellor on 5 January 1661, he was appointed to the newly erected commission of settlement on 12 April 1661 and was knighted on 23 April. He resigned as chief justice of Connacht on 5 September 1662. He died 8 May 1665 and was buried in Christ Church cathedral on 17 May.
He married first Anne (d. 1635), eldest daughter of Alderman Richard Barry (qv). By 1645 he had married Sarah, fourth daughter of Dr Jonas Wheeler (d. 1640), bishop of Ossory; they had a son, Nehemiah (qv), who became prime serjeant, baron, and chief baron of the exchequer.