O
- (Okpe) Oviri-Okpe
- (Ughelli North) Oviri-Ogor
- (Okpe) Oviri-Court
- (Sapele) Oviri
- (Ethiope East) Oviorie
- (Ughelli North) Ovhororo
- (Ughelli South) Oforigbala
- (Ughelli South) Ovhori
- (Ethiope West) Ovade
- (Ughelli South) Otutuama
- (Ethiope East) Otumara
- (Aniocha South) Otulu
- (Warri South) Otugbo
- (Isoko South) Otorofane
- (Ika North East) Otolokpo
- (Ughelli South) Otokutu
- (Isoko South) Otoka
- (Isoko North) Otibio
- (Isoko South) Oteri
- (Ughelli South) Otegbo
- (Ethiope East) Otefe
- (Ughelli South) Otor-Edo
- (Ndokwa East) Ossissa-Stat
- (Ndokwa East) Ossimilli
- (Ndokwa West) Osemele
- (Warri North) Orumegege
- (Burutu) Orugbene
- (Isoko South) Oruabe
- (Ethiope East) Orokpor
- (Ndokwa West) Orogun