Thomas O'Hagan, 1st Baron O'Hagan, KP, PC (Ire), QC (29 May 18121 February 1885), was an Irish lawyer and judge. He served as Lord Chancellor of Ireland from 1868 to 1874 and again from 1880 to 1881.
Background and education
O'Hagan was born in Belfast, the son of Edward O'Hagan, a merchant, and his wife Mary Bell, daughter of Captain Thomas Bell. He was educated at Royal Belfast Academical Institution, being in his day the only Catholic in the school. In 1836 he was called to the Irish Bar.
Career
Between 1838 and 1841 O'Hagan was the editor of The Newry Examiner. In 1840 he moved to Dublin, where he appeared for the repeal party in many political trials, becoming an Irish Queen's Counsel in 1849. His advocacy of a continuance of the Union with Great Britain, and his appointment as Solicitor-General for Ireland in 1860 and Attorney-General for Ireland in the following year, lost him the support of the Nationalist party, but he was returned to Parliament as Liberal Member of Parliament for Tralee in 1863. In 1865 he was appointed a judge of the Court of Common Pleas (Ireland), and in 1868 became Lord Chancellor of Ireland in William Ewart Gladstone's first administration. and held office until the resignation of the ministry in 1874. In 1880 he again became Lord Chancellor on Gladstone's return to office, but resigned in 1881.
thumb|200px|Sir Charles Monroe, 1st Baronet, who married Lord O'Hagan's daughter Mary
Lord O'Hagan died at Hereford House, London, in February 1885, aged 72, and was buried in Glasnevin Cemetery, Dublin. He was succeeded in the barony by his eldest son, Thomas (1878–1900), and then by another son, Maurice Herbert Towneley (born 1882).