Liam Ó Briain (16 September 1888 – 12 August 1974) was an Irish language expert and political activist. Born in North Wall, Dublin as William O'Brien, he took an interest in the Irish language from an early age and while still at the O'Connell School started using the Irish version of his name. He also attended meetings of the Gaelic League, then attended University College Dublin (UCD) on a scholarship, where he studied French, English and Irish, receiving a BA and an MA. On 1 September 1921 he married Helen Lawlor. The couple's only child was the journalist Eibhlín Ní Bhriain.