Though O’Brien was born in county Tipperary, his father settled in Dublin in the early 1800s and, following emancipation, became one of the city’s most prominent Catholic merchants. Following his father into the wine trade, O’Brien became the consul in Dublin for Spain and for Parma and Placentia. A ‘man of the people … and the architect of his own fortunes’ he engaged extensively in mercantile affairs and was a shipowner and director of several joint-stock companies.
O’Brien had joined the Catholic Association in the 1820s and later became an active member of the Repeal Association. As mayor of Dublin, he attracted popularity by daily escorting Daniel O’Connell to court during the state trial of 1844. He was chairman of the Irish Reform Club and in February 1846 was returned unopposed as a repealer at the Cashel by-election, which followed the resignation of the anti-repeal Liberal, Joseph Stock.
O’Brien became mayor of Dublin for a second time in 1849 and, after presenting the Queen with the keys of the city during her visit to Ireland, was created a baronet.
An Irish repealer, O’Brien only intermittently supported the Whig ministry, and was consistent in his opposition to its Irish habeas corpus suspension bill of 1848.
Having signed the memorial to the Treasury concerning relief on the debts owed by the Irish poor law unions, 29 Mar. 1852, O’Brien pledged himself to the policy of independent Irish opposition, and easily defeated a Conservative challenge at Cashel at that year’s general election, standing on a platform of poor law reform, state aid to Irish railways and manufacturing, and land reform, duly attending the tenant-right conference in August 1852.
Above all, O’Brien was committed to raising the social and political status of Irish Catholics and chaired a public meeting to protest against the inspection of nunneries bill, 27 Mar. 1854.
O’Brien died at his residence in Merrion Square, Dublin in December 1862, and was buried in the family mausoleum at Glasnevin cemetery, of which he had once taken an active part in the management.
