Máirtín Ó Muilleoir (né Martin Millar; born 1959) is an Irish Sinn Féin politician, author, publisher and businessman, who served as the 58th Lord Mayor of Belfast (2013–14). Ó Muilleoir's siblings include writer, blogger and Huffington Post columnist Adrian Millar, and journalist and editor Gerry Millar/Gearóid Ó Muilleoir of The Belfast Telegraph.