Former Owner
- M. Favia del Core1
- Magby, H1
- Manoel S. Pinto1
- Manuel Fernández del Castillo3
- Margaret of Croy1
- Maria Ludovica Favia del Core Borromeo1
- Mark Lansburgh1
- Martin Schøyen1
- Matteo Luigi Canonici7
- Matthaeus Lupin1
- McCormick Theological Seminary1
- Melchior Daniel Neubronner1
- Melk Abbey1
- Miguel de Mayora1
- Milt Freudenheim1
- Moissac Abbey1
- Monasterio de El Paular1
- Monastery at San Gregorio al Celio1
- Nathaniel Sherman Bouton1
- Novalesa Abbey1