O
- (Isoko South) Oroa-Emede
- (Isoko North) Orie
- (Ethiope East) Oriah
- (Ethiope East) Orhokpor
- (Ughelli North) Orhokpokpor
- (Ughelli North) Orho-Agbarho
- (Warri South) Orere
- (Ughelli South) Orere
- (Ughelli North) Oreba
- (Okpe) Opuraja
- (Warri North) Opuama
- (Udu) Opete
- (Ndokwa West) Opaetensm
- (Ndokwa East) Onya
- (Ndokwa East) Ononofu
- (Aniocha North) Onicha-Ugbo
- (Ughelli North) Onidjor Egbo-Uwheru
- (Aniocha North) Onicha-Ukwu
- (Aniocha North) Onicha-Olona
- (Ndokwa West) Onicha
- (Warri South) Omadino
- (Ethiope East) Olukobare
- (Isoko South) Olomoro
- (Aniocha South) Olodu
- (Bomadi) Olodiama
- (Warri South) Oleri
- (Warri North) Old Nana Town
- (Okpe) Okuidiemo
- (Oshimili South) Okwe
- (Ughelli South) Okwagbe Inland