Abraham Brewster PC (April 1796 – 26 July 1874) was an Irish judge and Lord Chancellor of Ireland.
Brewster was born at Ballinulta, the son of William Bagenal Brewster, of Ballinulta, County Wicklow, by his wife Mary, daughter of Thomas Bates. He received his earlier education at Kilkenny College, then proceeding to the University of Dublin in 1812, took his B.A. degree in 1817, and long after, in 1847, his M.A. degree.
Brewster was called to the Irish bar in 1819, and, having chosen Leinster for his circuit, soon acquired the reputation of a sound lawyer and a powerful speaker. Lord Plunket honoured him with a silk gown on 13 July 1835. Notwithstanding the opposition of Daniel O'Connell, he was appointed Law Adviser to the Lord Lieutenant of Ireland on 10 October 1841, and was Solicitor-General for Ireland from 2 February 1846 until 16 July. By the influence of his friend Sir James Graham, First Lord of the Admiralty, he was Attorney-General for Ireland from 10 January 1853 until the fall of the Aberdeen ministry on 10 February 1855.
Brewster was very active in almost all branches of his profession after his resignation, and his reputation as an advocate may be gathered from the pages of the Irish Law and Equity Reports, and in the later series of the Irish Common Law Reports, the Irish Chancery Reports, and the Irish Jurist, in all of which his name very frequently appears. Among the most important cases in which he took part were the Mountgarrett case in 1854, involving a peerage and an estate of £10,000 a year; the Carden abduction case in July of the same year; the Yelverton case, 1861; the Egmont will case, 1863; the Marquess of Donegall's ejectment action; and lastly, the great will cause of Fitzgerald v. Fitzgerald, in which Brewster's statement for the plaintiff is said to have been one of his most successful efforts.