Former Owner
- Mary Schell Collins1
- Mary W. T. Dickinson10
- Mary, Queen of Scots1
- Marymount College, Tarrytown4
- Matteo Barresi1
- Matteo Luigi Canonici16
- Matthew Bloxam1
- Matthew Donadski1
- Matthew Simpson Parkhurst1
- Matthias Corvinus1
- Maurice Johnson1
- Maurice Kann1
- Maximilian Henry of Bavaria1
- Mayfair Rare Books and Manuscripts1
- Melk Abbey2
- Menno Hertzberger1
- Mercantile Library Company1
- Merlemont family1
- Meschatin La Faye family1
- Michael Greenberg5