| Title | Call No. | Location | Notes | Subject |
| Oikumene (Vol.1-5) | DE 1 O37 | PCL | Discontinued | Classical Studies |
| Omnibus | alpha | Class | Classical Studies | |
| Opus (1982-1992) | HC 31 O687 | PCL | Discontinued | Classical Studies |
| Opuscula Romana (Vol.1-14) | 913.37 Op72 | PCL | Ancient History, Classical Studies | |
| Opuscula Romana (Vol.15- ) | DG 12 S815 | PCL | Ancient History, Classical Studies | |
| Oxford Journal of Archaeology | CC 1 O946 | PCL | Also Online | Archaeology |
| Oxford Studies in Ancient Philosophy | B 1 O936 | PCL | Philosophy |