Sir James Donnellan (c. 1588 – 1665) was an Irish lawyer and politician, who became Chief Justice of the Irish Common Pleas in 1660. He was unusual among the Irish judges of the time in being of Gaelic descent; and more remarkable in that his service as a judge under Oliver Cromwell did not disqualify him from service after the Restoration of Charles II.
He was the third son of Nehemiah Donnellan, Archbishop of Tuam, and his wife Elizabeth O'Donnell. He married firstly Anne Barry, sister of James Barry, 1st Baron Barry of Santry and secondly Sarah Wheeler, daughter of Jonas Wheeler, Bishop of Ossory. By Sarah he was the father of Nehemiah Donnellan, Chief Baron of the Irish Exchequer and also of several daughters. Nemehiah was the father of Anne Donnellan, who founded the Donnellan lectures in Trinity College Dublin, and Katherine Donnellan, who married Robert Clayton, Bishop of Cork and Ross. James's principal residence was at Rathswire in County Westmeath. He is buried in Christchurch Cathedral, Dublin.
He had a distinguished career at Trinity College Dublin which he was later to represent in the Irish House of Commons. He was scholar in 1607, Bachelor of Arts in 1610, Fellow in 1612 and Master of Arts in 1613.