- Ōakasawa
- Ōaratomachi
- Ōbazawa
- Obiori
- Obirō
- Ōbuchi
- Ōdai
- Ōdaira
- Ōtaira
- Ōdomari
- Ōdōri
- Ōgata-honchō
- Ogi
- Ogi
- Ogi-kaneta-shinden
- Ogi-kinoura
- Ogi-kowashimizu
- Ogi-ōura
- Ogibori
- Ogimachi
- Ōgoto
- Ogunimachi-ainohara
- Ogunimachi-nanokamachi
- Ogunimachi-nihon’yanagi
- Ogunimachi-ōgai
- Ogunimachi-yamanota
- Ōhirota
- Ōishi
- Ojiya
- Okashinden