Barnewall, Sir Nicholas (1592–1663), 1st Viscount Barnewall of Kingsland , politician, was son of Sir Patrick Barnewall, of Turvey, Gracedieu, and Fieldstown, Co. Dublin, and his wife Mary, daughter of Sir Nicholas Bagenal (qv). Sir Patrick Barnewall (qv) (d. 1552) was his great-grandfather.
Nicholas Barnewall was educated at Douai in the Spanish Netherlands, and entered Gray's Inn, London, on 15 August 1611. On his father's death (1623) he inherited substantial property, which he augmented by land deals; by 1641, for instance, he held over 2,000 acres in Co. Roscommon. Prominent among catholic Old English gentry and with many connections to them and to influential New English and Gaelic families – his sister married Rory O'More (qv) – he was active in local affairs around his home at Drimnagh, Co. Dublin. In 1625 he signed a petition to the king by the lords of the Pale; was nominated, as one of several predominantly catholic gentry, to command ‘trained bands’ in the Pale; and was a member of the commission of the peace for Co. Dublin. He became a freeman of the city of Dublin in 1629.
Barnewall sat for Co. Dublin in the parliaments of 1634–5 and 1640–47. On 11 November 1640 he was one of seven Old English MPs appointed to represent Irish grievances to the king; and five months later he was one of eight prominent signatories of the petition and offer to Charles I from the inhabitants of Connacht, Clare, Tipperary, and Limerick. When the 1641 rebellion began, Barnewall was appointed governor of Co. Dublin and was authorised to raise and command a force of 300 men to defend the county; but after travelling to London with the government's permission, he took refuge with his wife in Wales till 1643/4. Family connections and personal sympathies alike linked him to the catholic cause; however, his readiness to shelter protestant refugees, together with his general adherence to English interests (and, perhaps, the goodwill of Queen Henrietta, a catholic) gained him the titles of baron of Turvey and Viscount Barnewall of Kingsland (29 June 1646), and his actions in the 1640s may later have stood to his credit under the Cromwellian regime. He was imprisoned in 1654 for complicity in a plot against the protector, and his property in Leinster was sequestrated (1656); however, his transplantation to Connacht seems to have been left unenforced, and his Roscommon property remained in his hands throughout. At the restoration of the monarchy (1660), Barnewall was again in London representing Irish catholic interests. The Leinster property was restored to him in 1660, and he had fully recovered his estates by the time of his death at Turvey on 20 August 1663. He was buried at Lusk church, Co. Dublin, on 3 September; his third son, Henry, succeeded him in the titles.
He married (a.7 July 1617) Bridget (d. p.1660), daughter of Henry Fitzgerald (qv), 12th earl of Kildare, and widow of Rory O'Donnell (qv) (Ruaidhrí Ó Domhnaill), earl of Tyrconnell. They had five sons – the eldest, Patrick, served as a colonel of royalist horse in England during the civil wars – and four daughters, including Mabel, who married Christopher Plunkett (qv), 2nd earl of Fingall.