Born in Carrick-on-Suir, County Tipperary O'Brien became a Home Ruler nationalist and an anti-liberal ultramontanist fashioned after Pope Pius IX. At the age of two when his father died his mother sold the family grocery business and they moved to Limerick. He was educated locally at St. Marys in Limerick, and at Knockbeg college, Carlow. He studied for the priesthood in Maynooth College graduating with distinction, he was ordained then in 1839. As a writer he contributed to The Irish Catholic Magazine, the Irish Monthly and The Nation. In 1849 he founded the Catholic Young Men's Society in order to help Catholics advance their area of religious interests. He also wrote novels, often portraying moral dilemmas. O'Brien was president of Saint Mary's College, in Halifax, Nova Scotia, Canada from 1840-45.
He is buried in Newcastle West.
O'BRIEN FOUNDED SAINT MARY'S COLLEGE in Halifax in 1839 along with Fr Launence Dease. Halifax Newspapers