Sir Nicholas Walsh (1542–1615) was an Irish judge, politician and landowner of the late Tudor and early Stuart era. He was Speaker of the Irish House of Commons in the Parliament of 1585–6 and a close ally of the Lord Deputy of Ireland, Sir John Perrot. Perrot's downfall almost ruined Walsh but he soon regained his influence, as he was noted for his loyalty to the Crown. He later became Chief Justice of the Irish Common Pleas. He sat on the Privy Council of Ireland in a role which has been compared to that of Minister without portfolio. His loyalty to the Crown led to his narrowly escaping death during a riot in 1603. He acquired a great fortune and was called "the richest commoner in Munster". The well known Irish poem, Labhrann ar Iongaibh Éireann, by Tuileagna Ó Maoil Chonaire, was addressed to him.
He was born at Waterford, son of James Walsh, Mayor of Waterford in 1539 and 1547, and grandson of Patrick Walsh, who was also Mayor of the town. His father died while still a young man, and Nicholas and his sister were entrusted to the care of Thomas Butler, 10th Earl of Ormond, who sent him to live in the household of Nicholas White, later Master of the Rolls in Ireland. The Walsh family was wealthy, and this no doubt was the foundation of Nicholas's great fortune. He was studying law at Lincoln's Inn in 1561.
His sister Johanna married another protégé of the Earl of Ormond, Gerald Comerford, who like Nicholas went on to become a trusted Crown official and a High Court judge, but died, still a relatively young man, in 1604.