| Keyword | Type | See | See also | Notes |
|---|---|---|---|---|
| Orisha | Keyword | |||
| Orissa | Place | Odisha | ||
| Orixa | Keyword | Orisha | ||
| Oriya | Ethnic group | |||
| Orkney Islands | Place | |||
| Orma | Ethnic group | |||
| Ormuri | Ethnic group | |||
| Ornaments | Keyword | |||
| Orok | Ethnic group | |||
| Orokaiva | Ethnic group | |||
| Oromo | Ethnic group | |||
| Oromo language | Keyword | |||
| Oron | Ethnic group | |||
| Oronao | Ethnic group | Wari' | ||
| Orongo site | Place | |||
| Orphans | Keyword | |||
| Orphism | Keyword | |||
| Orthodox Eastern Church | Keyword | |||
| Orthography and spelling | Keyword | |||
| Oryol Oblast | Place | Russian Federation | ||
| Osage | Ethnic group | |||
| Osetin | Ethnic group | |||
| Oslo | Place | |||
| Ossetia | Place | |||
| Ossuaries | Keyword | |||
| Osteitis deformans | Keyword | |||
| Osteoarthritis | Keyword | |||
| Osteoporosis | Keyword | |||
| Ostrakha | Keyword | |||
| Ostyak | Ethnic group | KHant | ||
| Otavalo | Ethnic group | |||
| Otavipithecus namibiensis | Keyword | |||
| Other | Ethnic group | |||
| Other-than-human | Keyword | |||
| Oto | Ethnic group | |||
| Otomanguean languages | Keyword | |||
| Otomani culture | Keyword | |||
| Otomi | Ethnic group | |||
| Otomi language | Keyword | |||
| Otrar sites | Place | |||
| Ottawa | Ethnic group | |||
| Ottawa | Place | |||
| Ottoman empire | Keyword | |||
| Ottoman period | Keyword | |||
| Oudepost I site | Place | |||
| Ovambo | Ethnic group | |||
| Ovarian cancer | Keyword | |||
| Ovens | Keyword | |||
| Overton Hill site | Place | |||
| Ovimbali | Ethnic group | Mbundu |