Máirtín Ó Muilleoir MLA (['m?a???t?i?n? o? 'm?i?l?o???] born Martin Millar; 1959) is an Irish Sinn Féin politician, author, publisher and businessman, who served as the 58th Lord Mayor of Belfast (2013–14).
Ó Muilleoir has two siblings, one of which is writer, blogger and Huffington Post columnist Adrian Millar, whilst the other is journalist and editor Gerry Millar/Gearóid Ó Muilleoir of The Belfast Telegraph.