James O'Brien (died 24 April 1916) was a Royal Irish Constabulary policeman who was stationed at the gates of Dublin Castle during the 1910s. He was a respected figure in the community, with the typist May Lacy frequently conversing with him on her way to work. On 23 April 1916, at the start of the Easter Rising, he was confronted by a squad of ICA soldiers who demanded entry into the castle. O'Brien refused, even after their officer Sean Connolly warned him and cocked a pistol. O'Brien stood silently until Connolly shot O'Brien in the heart, mortally wounding him; Elizabeth Butler tried to tend to him, horrified at the shooting of an unarmed man by the rebels, and O'Brien's last words were "Bless me Father, for I have sinned."