Dukes | Titles by Rank
- Dukes of Mecklenburg-Schwerin
- Dukes of Medina de las Torres
- Dukes of Medina de Rioseco
- Dukes of Medina Sidonia
- Dukes of Medinaceli
- Dukes of Melfi
- Dukes of Melfort
- Dukes of Melito
- Dukes of Meran
- Dukes of Meranien
- Dukes of Mercoeur
- Dukes of Milan
- Dukes of Miranda do Corvo
- Dukes of Miranda-E
- Dukes of Miranda-I
- Dukes of Mirandola
- Dukes of Moctezuma de Tultengo
- Dukes of Modena
- Dukes of Mödling
- Dukes of Mola
- Dukes of Mondgragone
- Dukes of Mondragone
- Dukes of Monmouth
- Dukes of Montagu
- Dukes of Montalbano
- Dukes of Montalto-I
- Dukes of Montalto-S
- Dukes of Montault
- Dukes of Montbazon
- Dukes of Monte Marciano
- Dukes of Montealegre
- Dukes of Montebello
- Dukes of Monteleón
- Dukes of Monteleone
- Dukes of Montellano
- Dukes of Montemar
- Dukes of Monterano
- Dukes of Monterotonda
- Dukes of Monterotondo
- Dukes of Montferrat
- Dukes of Montmorency-I
- Dukes of Montmorency-II
- Dukes of Montmorency-III
- Dukes of Montmorency-Laval
- Dukes of Montoro
- Dukes of Montpensier
- Dukes of Montpensier-e
- Dukes of Montrose
- Dukes of Morella
- Dukes of Morignano