O
- (Province of Zambales) Oyong
- (Province of Nueva Ecija) Osmeña Student
- (Province of Bulacan) Osboy
- (Province of Tarlac) Oloybuaya
- (Province of Tarlac) O’Donnell
- (Province of Aurora) Ontok
- (Province of Nueva Ecija) Olivete
- (Province of Tarlac) Orebat
- (Province of Nueva Ecija) Ocampo-Rivera District
- (Province of Bataan) Old San Jose
- (Province of Nueva Ecija) Obrero
- (Province of Tarlac) O’Donnell
- (Province of Bataan) Orani
- (Province of Bataan) Orion
- (Province of Bulacan) Obando
- (Province of Zambales) Olóngapo