The Catholic Encyclopedia O Frederick Oakeley O Antiphons Oates's Plot Oaths English Post-Reformation Oaths Oaxaca Monastery of Obazine Obba Obedience Religious Obedience Obedientiaries Oblate Sisters of Providence Oblates of Mary Immaculate Oblates of Saint Francis de Sales Oblati Obligation Tighernach O'Braein Obregonians Obreption Terence Albert O'Brien David O'Bruadair Vatican Observatory Edmund Bailey O'Callaghan Torlogh O'Carolan William of Ockham Occasionalism Occasions of Sin Thomas Occleve Occult Art, Occultism Occurrence Vicariate Apostolic of Central Oceania Daniel O'Connell Charles O'Conor Charles O'Conor Octave Octavarium Romanum Gelasius O'Cullenan Eugene O'Curry Daniel O'Daly Donogh Mór O'Daly Ancient See of Odense in Denmark Carlo Odescalchi O Deus Ego Amo Te Cornelius O'Devany St. Odilia St. Odilo John Mary Odin Walter Odington St. Odo St. Odo Edmund O'Donnell John O'Donovan Bl. Odo of Cambrai Odo of Canterbury Odo of Cheriton Odo of Glanfeuil John O'Dugan Joseph O'Dwyer John Œcolampadius Episcopal Oeconomus Œcumenius John James Maximilian Oertel Oettingen Offa Offerings Offertory Divine Office Office of the Dead Maurice O'Fihely O Filii et Filiæ Diocese of Ogdensburg Marco D'Oggione Ven. John Ogilvie Ogliastra Eugene O'Growney John O'Hagan Thomas O'Hagan John O'Hanlon Theodore O'Hara Patrick O'Hely Thomas O'Herlahy O'Higgins Ohio Aloys Karl Ohler Dermond O'Hurley Maelbrighte O'Hussey Oil of Saints Holy Oils Ointment in Scripture Alonso de Ojeda Jean d'Okeghem Oklahoma St. Olaf Haraldson Nicolaus Oláh Olba Old Catholics The Old Chapter Ven. Edward Oldcorne Oldenburg Old Hall (St. Edmund's College) Hugh Oldham Augustino Oldoini The Old Testament Canon of the Old Testament Arthur O'Leary Olenus Zbigniew Olesnicki Jean-Jacques Olier Olinda Oliva Gian Paolo Oliva Pierre Olivaint George Oliver Mount Olivet Olivetans Pierre Jean Olivi Olivier de la Marche Léon Ollé-Laprune Olmütz Michael O'Loghlen St. Olympias Olympus Diocese of Omaha Ombus Kathleen O'Meara St. Omer Omission Omnipotence Hugh O'Neill Owen Roe O'Neill Onias Ontario Ontologism Ontology Shrine of Oostacker Collect Ophir Oporto Gilles-Marie Oppenordt Oppido Mamertina St. Optatus Optimism Right of Option Malachias O'Queely Oracle Oran Councils of Orange Orange Free State Vicariate Apostolic of Orange River Orans Orate Fratres Oratorio Oratory The Oratory of Saint Philip Neri French Congregation of the Oratory Nicolas d'Orbellis Orcagna Orcistus Ordeals Ordericus Vitalis Holy Orders The Military Orders Ordinariate Ordinary Ordines Romani Oregon Archdiocese of Oregon City Bernard O'Reilly Edmund O'Reilly Edmund O'Reilly Hugh O'Reilly John Boyle O'Reilly Myles William Patrick O'Reilly Oremus Diocese of Orense Nicole Oresme Organ The Organic Articles Diocese of Oria Barnaba Oriani Oriental Study and Research Orientation of Churches Orientius Oriflamme Origen and Origenism Original Sin Orihuela St. Joseph Oriol Oristano Orkneys Niccolò Orlandini Diocese of Orléans Councils of Orléans Barent Van Orley Philibert de l'Orme Oropus Patrick Henry O'Rorke Paulus Orosius Orphans and Orphanages Giuseppe Agostino Orsi Orsini Orsisius Abraham Ortelius Orthodox Church Orthodoxy Feast of Orthodoxy Orthosias Ortolano Ferrarese Orval Orvieto Matthieu Ory Osaka O Salutaris Hostia Osbald Ven. Edward Osbaldeston Osbern Oscott (St. Mary's College) Osee Osimo Ancient See of Oslo in Norway Diocese of Osma St. Osmund Diocese of Osnabrück Arnaud d'Ossat Diocese of Ossory Ostensorium (Monstrance) Ostia and Velletri Ostiensis Ostracine Christian Ostraka Ostrogoths Philip O'Sullivan Beare St. Oswald St. Oswald St. Oswin Otfried of Weissenburg Othlo St. Othmar Marcus Salvius Otho St. Lawrence O'Toole Otranto Ottawa University of Ottawa St. Otto Otto I, the Great Otto II Otto III Otto IV Ottobeuren Otto of Freising Otto of Passau Otto of St. Blasien St. Ouen The Lord's Prayer Feast of Our Lady, Help of Christians Our Lady of Charity of the Good Shepherd Feast of Our Lady of Good Counsel Brothers of Our Lady of the Fields Our Lady of the Snow Our Lady of Perpetual Succour Friedrich Overbeck Bernhard Heinrich Overberg Theories of Population Diocese of Oviedo Nicholas Owen John Oxenford Henry Nutcombe Oxenham Oxford University of Oxford The Oxford Movement (1833-1845) Oxyrynchus Antoine-Frédéric Ozanam Jacques Ozanam Ozias