Background
He was the oldest son of Richard Southwell, son of Sir Thomas Southwell, 1st Baronet, and his wife Lady Elizabeth O"Brien, daughter of Murrough O"Brien, 1st Earl of Inchiquin.
He was the oldest son of Richard Southwell, son of Sir Thomas Southwell, 1st Baronet, and his wife Lady Elizabeth O"Brien, daughter of Murrough O"Brien, 1st Earl of Inchiquin.
Southwell was also imprisoned, however released and pardoned in the following year. In 1695, Southwell entered the Irish House of Commons for Limerick County, representing it until 1713. He was returned for the constituency again from 1715 until August 1717, when he was elevated to the Peerage of Ireland as Baron Southwell, of Castle Mattress, in the County of Limerick.
In 1697, Southwell became a Commissioner of the Revenue, however resigned in 1712.
He was reappointed two years later and held this post until his death in 1720. In May 1710, Southwell was sworn of the Privy Council of Ireland.
Southwell died at Dublin and was buried at Rathkeale.