John Lysaght, 1st Baron Lisle of Mountnorth, in the County of Cork (1702 – 15 July 1781), was an Irish peer in the Peerage of Ireland and a politician.
The eldest son of Nicholas Lysaght and Grace, daughter of Colonel Thomas Holmes of Kilmallock, County Cork, John was educated at Trinity College, Dublin.
His father Nicholas was a Protestant landowner in southern Ireland, a soldier he served with William III's invading Orange army at the Battle of Boyne in 1689 as a Colonel of Horse.
The ensuing row in the House of Commons precipitated the fall of the Earl of Strafford, and the opening conflict of the English Civil War the following year.
John Lysaght sat as a Member of the Irish House of Commons for Charleville from 1727 until 1758, when on 18 September he was raised to the Peerage of Ireland as Baron Lisle, of Mountnorth in the County of Cork.