|A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|Y|Z| O'Daly, Carroll (Cearbhall Ó Dálaigh) O'Kelly, Sean Thomas (Seán Tomás Ó Ceallaigh) Obama, Barack Obregón, Álvaro Oman: Archontology Oman: Heads of State: 1749-2021 Oman: Notes Oman: Polity Style: 1749-2021 Oman: Sources Orange Free State: Archontology Orange Free State: Heads of State: 1854-1902 Orange Free State: Polity Style: 1854-1902 Orange Free State: Sources Order of Malta: Archontology Order of Malta: Grand Masters: 1530-1798 Order of Malta: Grand Masters: 1798-1803 Order of Malta: Grand Masters: 1803-2021 Order of Malta: Official Style: 1530-2021 Order of Malta: Sources ORLÉANS, Louis-Philippe d' Ortiz Rubio, Pascual Osorio de Moscoso, Vicente Isabel (Marqués de Astorga) Ottoman Empire: Archontology Ottoman Empire: Notes Ottoman Empire: Polity Style: 1453-1922 Ottoman Empire: Rulers: 1453-1922 Ottoman Empire: Sources |A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|Y|Z| Last updated on: 12 Apr 2021 14:00:28