Background
O'Brien was the son of Sir Edward O'Brien, 2nd Baronet and his wife Mary Hickman, inheriting the baronetcy on the death of his father in 1765.
Member of Parliament in the Parliament of Ireland
O'Brien was the son of Sir Edward O'Brien, 2nd Baronet and his wife Mary Hickman, inheriting the baronetcy on the death of his father in 1765.
In 1761, he entered the Irish House of Commons as the member for Ennis, sitting until 1768. Subsequently O'Brien successfully ran for Clare, a seat previously held by his father, holding it until 1776. In the election of 1783, he became the representative for Tuam.
O'Brien was sworn of the Privy Council of Ireland in 1786. He served for the latter constituency until 1790, when he was re-elected for Ennis. He held this seat finally until his death in 1795.
[Royal Society]
He was then again elected for Ennis, but following the unseating of Hugh Dillon Massy as Member of Parliament for Clare, O'Brien returned to represent that constituency in 1778.