Parentless Concepts
- Austrian Academy of Sciences
- Austrian Exchange Service
- Austrian Research Foundation
- Austrian Research Promotion Agency
- National Fund of the Republic of Austria for Victims of National Socialism
- Ostermayer, Gerardus
- Ostermayr, Gerhard
- other
- Otto of Freising
- Otto, Julius Konrad
- Ottokar I
- Ovid, Fasti
- Oxford
- P. Caietanus
- P. Carl
- P. Ferdinandus
- P. Flavius
- P. Henricus
- P. Hillin
- P. Martinus
- P. Maximilianus
- P. Nazarithanus
- P. Stanislaus
- P. Thomas
- P. Valentinus