Olau - Padu
- Olaus Magnus
- Olba
- Old Catholics
- Old Chapter, The
- Old Hall (St. Edmund's College)
- Old Law
- Old Testament
- Old Testament, Canon of the
- Oldcorne, Ven. Edward
- Oldenburg
- Oldham, Hugh
- Oldoini, Augustino
- Olenus
- Olesnicki, Zbigniew
- Olier, Jean-Jacques
- Olinda
- Oliva
- Oliva, Gian Paolo
- Olivaint, Pierre
- Oliver Almond
