O'Brennan, Martin Andrew (1812–78), newspaper editor, was born in Co. Mayo, ninth or eleventh son of Martin O'Brennan (occupation unknown) and Sarah O'Brennan (née Cullen). He was educated in St Jarlath's College, Tuam, and came to Dublin c.1836, where he apparently worked for the repeal movement and was secretary without pay to Fr Theobald Mathew (qv) By the 1850s he was running a school for young men studying to enter university, civil, or military positions and had embarked on a career as an amateur historian, chiefly preoccupied with Irish history and language. His Antiquities of ancient Ireland (1858) sold out in two months; Douglas Hyde (qv) owned a copy although he had a low opinion of O'Brennan as an Irish scholar. In 1857 he entered the King's Inns and the next year was admitted to Gray's Inn, but was never called to the bar. The following year he returned to Tuam and founded the Connaught Patriot and Tuam Advertiser, whose first edition appeared 27 August 1858. It was a catholic, nationalist paper dealing with local news, markets, and poetry, and supporting the revival of the Irish language. O'Brennan urged professors of Irish to begin teaching directly rather than confining themselves to antiquarian study, and he personally explored the origin of the Gaelic race and their settlement in Ireland over numerous editions of the paper. In economic matters he preached protectionism and acclaimed the completion of Tuam railway terminus (1859) because the stones came from a local quarry. The following year, when plans were being promulgated to erect a Dublin statue of Daniel O'Connell (qv), O'Brennan advocated the use of peat as building material because cutting the bog would provide work for young Irish people and prevent their emigration to England ‘where their mortality [sic] would be in danger’ (Connaught Patriot, 28 Aug. 1860).
His return to Tuam had coincided with the appointment of the radical priest Fr Patrick Lavelle (qv) as administrator and parish priest at Partry. The two shared political sympathies: Lavelle was vice-president of the National Brotherhood of St Patrick, an organisation affiliated to the Fenians, which O'Brennan supported in speeches and articles. The Connaught Patriot was in many ways the mouthpiece of Lavelle, who used it to mount a campaign against Thomas Plunket (qv), the Church of Ireland bishop of Tuam, and to criticise Cardinal Paul Cullen (qv). Bishop MacEvilly described the paper as ‘a malicious Garibaldian rag which is sometimes heretical, sometimes schismatical, and at all times personally offensive to the head of the church’ (Norman, 102). O'Brennan therefore raised the hostility of the church without gaining the support of the Fenians. Thomas Luby (qv) and James Stephens (qv) thought him a fool and nicknamed him ‘Mary-Anne’. In 1864 Luby reviewed Brennan's Ancient Ireland in the Irish People, and described it as a ‘literary Leviathan . . . the reader never knows exactly where he is or at what age of the world; so rapid and unceasing are the learned doctor's changes of place and time’ (Legge, 105). Lavelle remonstrated with Luby, to no avail. Dublin Castle eventually arrested O'Brennan in October 1865 for articles declaring that all catholics were free to join the Fenians and that Irishmen serving in the British army had the right to disobey orders of an unjust government. O'Brennan pleaded guilty to the charge of sedition and was released, to be rearrested in March 1866 for uttering seditious language, and again released. A year later he was in London editing a newspaper, the Irish News, which ran for four issues (March–April 1867). It included testimonials to Fr Lavelle and an attack on James Stephens. It was seized on 13 April 1867, after which he emigrated to America. He died in Chicago on 7 March 1878, leaving destitute a widow and eight children.