Former Owner
- Madeleine Cosman1
- Maggs Bros Ltd1
- Malachia Ormanian1
- Malvezzi de' Medici1
- Mannucci family1
- Manūchihr Nukhastīn Āṣaf Qājār1
- Marcianus F. Rossi1
- Mario Maffei1
- Mark Augspürger1
- Mark Lansburgh1
- Markus Fugger1
- Mary Augusta Strachey1
- Mary Schell Collins1
- Matthias Corvinus1
- Maurilio Morazio1
- Maximilian Henry of Bavaria1
- Mayer Sulzberger1
- Mazliah Finzi1
- Melk Abbey1
- Merlemont family1