Dukes | Titles by Rank
- Dukes of Lorges
- Dukes of Lorraine
- Dukes of los Castillejos
- Dukes of Losada
- Dukes of Loulé
- Dukes of Lower-Bavaria
- Dukes of Lübeck
- Dukes of Lüben
- Dukes of Lucca
- Dukes of Lucera
- Dukes of Lugo
- Dukes of Luna
- Dukes of Luxemburgo
- Dukes of Luynes
- Dukes of Macedonia
- Dukes of Maddaloni
- Dukes of Madrid
- Dukes of Maestrazgo
- Dukes of Magenta
- Dukes of Mahon
- Dukes of Mähren-Brünn
- Dukes of Maillé
- Dukes of Maine
- Dukes of Makovica
- Dukes of Manchester
- Dukes of Mandas y Villanueva
- Dukes of Mantua
- Dukes of Maqueda
- Dukes of Marchena
- Dukes of Marigliano
- Dukes of Marlborough
- Dukes of Marmier
- Dukes of Marsi
- Dukes of Martina
- Dukes of Marzano
- Dukes of Masóvia
- Dukes of Massa
- Dukes of Maura
- Dukes of Mayenne
- Dukes of Mayra
- Dukes of Mazarin
- Dukes of Mazarino
- Dukes of Mecklemburg
- Dukes of Mecklemburg-Gadebusch
- Dukes of Mecklemburg-Grabow
- Dukes of Mecklemburg-Güstrow
- Dukes of Mecklemburg-Ivernack
- Dukes of Mecklemburg-Mirow
- Dukes of Mecklemburg-Stargard
- Dukes of Mecklemburg-Strelitz