O
- (Province of Pangasinan) Oraan East
- (Province of Pangasinan) Oda
- (Province of La Union) Obug
- (Province of Pangasinan) Oboyoboy
- (Province of Pangasinan) Obong
- (Province of La Union) Oaquing
- (Province of Ilocos Sur) Oalin
- (Province of Ilocos Sur) Oaig Daya
- (Province of Ilocos Norte) Oaig
- (Province of Pangasinan) Ouou
- (Province of Pangasinan) Oraan West
- (Province of Pangasinan) Osmena
- (Province of Pangasinan) Okcuanan
- (Province of Ilocos Sur) Olo-Olo Sur
- (Province of Pangasinan) Osmena Sr.
- (Province of Pangasinan) Ottama
- (Province of Pangasinan) Olo Cafabrosan
- (Province of Pangasinan) Olo Cagarlitan
- (Province of Pangasinan) Olanen
- (Province of Pangasinan) Omando
- (Province of Ilocos Norte) Otol
- (Province of Ilocos Sur) Otol
- (Province of Ilocos Sur) Oso
- (Province of Pangasinan) Osiem
- (Province of Ilocos Sur) Ortoc
- (Province of La Union) Ortega
- (Province of Ilocos Sur) Oribi
- (Province of Ilocos Sur) Orence
- (Province of Ilocos Sur) Ora
- (Province of Pangasinan) Ontambo