O
- (North) Obrechies
- (Pas-de-Calais) Ouve
- (Pas-de-Calais) Ostrel
- (North) Ovillers
- (North) Ossu
- (Pas-de-Calais) Ostrohove
- (Aisne) Outre
- (North) Oxelaere
- (Somme) Ouville
- (North) Outtersteene
- (Somme) Oust-Marest
- (Aisne) Oulches-la-Vallée-Foulon
- (Pas-de-Calais) Ostove
- (North) Ostergnies
- (Oise) Orsimont
- (Oise) Ormoy-Villers
- (Somme) Offoy
- (Oise) Ognes
- (North) Ohain
- (Pas-de-Calais) Olhain
- (Pas-de-Calais) Olincthun
- (Somme) Offeux
- (Pas-de-Calais) Onglevert
- (Somme) Onicourt
- (Somme) Onival
- (Somme) Orival
- (Pas-de-Calais) Orlencourt
- (Aisne) Orgeval
- (Somme) Offignies
- (Oise) Offoy