Sir Nicholas Barnewall (died after 1465) was an Irish judge and landowner of the fifteenth century: he was the ancestor of the Barnewall Baronets, of Crickstown.
He was born at Crickstown, County Meath, the eldest son of Sir Christopher Bernevall (died 1446) and his wife Matilda (or Maud) Drake, a widow whose first husband belonged to the wealthy Drake family of Drakerath ,whose most notable member was John Drake, who was three times Lord Mayor of Dublin in the early 1400s, and led the citizens of Dublin to a decisive victory over the O'Byrne clan of County Wicklow at the Battle of Bloody Bank in 1402.
His father was Lord Chief Justice of Ireland for more than a decade. Nicholas was "bred up to the law", and was appointed to the same office as his father in 1457, with a knighthood. In 1461 he was superseded in favour of Sir Thomas Fitz-Christopher Plunket, but regained office later the same year. He retired about 1463, and was still alive in 1465.
He married Ismay, daughter and co-heiress of Sir Robert Serjeant of Castleknock, County Dublin: they had at least two sons, Christopher and Edmund. Ismay's sister Joan married Sir Jenico d"Artois the younger; there is said to have been a bitter dispute over the inheritance between the two sisters and their respective husbands, from which the Barnewalls emerged the winners, acquiring far more than the half of the estate which Ismay was entitled to..
Christopher, Nicholas's eldest son, inherited Crickstown, where the Barnewall family remained for several generations. He married Ellen Butler, daughter of Pierce Butler, Baron Dunboyne. In 1623 his descendant Sir Patrick Barnewall was conferred with a baronetcy, which still exists.
Ismay outlived her husband, and remarried the prominent Yorkist nobleman Sir Robert Bold, 1st and last Baron Ratoath, who died in 1479. Catherine Bold, Lord Ratoath's daughter and heiress by his previous marriage, married Ismay's younger son Edmund Barnewall: they settled at Dunbrow in County Dublin, where their descendants remained for several generations.
Nicholas's younger brother Robert was created the first Baron Trimleston in 1461.