Marquesses | Titles by Rank
- Marquesses of Oropesa
- Marquesses of Oroquieta
- Marquesses of Ortona
- Marquesses of Osera
- Marquesses of Otero
- Marquesses of Otero de Herreros
- Marquesses of Otero de Herreros
- Marquesses of Ovieco
- Marquesses of Oyra
- Marquesses of Pacheco
- Marquesses of Palacios
- Marquesses of Palaminy
- Marquesses of Pallars
- Marquesses of Palmela
- Marquesses of Palmerola
- Marquesses of Palomares de Duero
- Marquesses of Pandino
- Marquesses of Pange
- Marquesses of Panisse Passis
- Marquesses of Panisse-Passis
- Marquesses of Paradas
- Marquesses of Paraná
- Marquesses of Paranaguá
- Marquesses of Paredes
- Marquesses of Pascarolla
- Marquesses of Paterna del Campo
- Marquesses of Paysac
- Marquesses of Pazo de la Merced
- Marquesses of Pedroso de Lara
- Marquesses of Pelayo
- Marquesses of Pembroke
- Marquesses of Peña Plata
- Marquesses of Peñacerrada
- Marquesses of Peñafiel
- Marquesses of Penafiel
- Marquesses of Peñaflor
- Marquesses of Peñafuente
- Marquesses of Peñafuerte
- Marquesses of Peñalba
- Marquesses of Penalva
- Marquesses of Perales del Rio
- Marquesses of Peralta
- Marquesses of Percile
- Marquesses of Pereira Coutinho
- Marquesses of Perijáa
- Marquesses of Persan
- Marquesses of Pérusse des Cars
- Marquesses of Pescara
- Marquesses of Peveragno
- Marquesses of Piancastagnajo