Former Owner
- Matthew Simpson Parkhurst1
- Matthias Corvinus1
- Maurice Johnson1
- Maurice Kann1
- Maximilian Henry of Bavaria1
- Mayfair Rare Books and Manuscripts1
- Menno Hertzberger1
- Mercantile Library Company1
- Merlemont family1
- Meschatin La Faye family1
- Michael M. Zagayski1
- Michael Wodhull1
- Michaeliskonvent1
- Michel Chasles1
- Michel Ferdinand d'Albert d'Ailly1
- Michel de Léon1
- Michiel family1
- Middle Hill Rare Books & Manuscripts AB (Stockholm, Sweden)1
- Mikhail Golitsyn1
- Millard Meiss1