Eimar Ultan O'Duffy (29 September 1893 - 21 March 1935) was born in Dublin and educated at Belvedere College in Dublin, Stonyhurst College in Lancashire and at University College Dublin. He and Bulmer Hobson caused disaster to the plans for the 1916 Easter Rising when they told Eoin MacNeill that the Rising was planned for the next week; MacNeill, nominal head of the Irish Volunteers, reacted by sending messengers around the country to call off the manoeuvres which were the cover for the Rising, and advertising in newspapers to cancel them. O'Duffy and Hobson went to the North.