Former Owner
- Marie de Albano1
- Marilyn Carbonell1
- Mario Maffei1
- Martin Breslauer1
- Martin Picker2
- Martin Schøyen4
- Mary W. T. Dickinson4
- Matteo Barresi1
- Matteo Luigi Canonici13
- Mayfair Rare Books and Manuscripts1
- Mazliah Finzi1
- Melk Abbey1
- Mercantile Library Company1
- Michael Bernays1
- Michael Greenberg2
- Michael Tomkinson1
- Michel Chasles1
- Michel Ferdinand d'Albert d'Ailly1
- Middle Hill Rare Books & Manuscripts AB (Stockholm, Sweden)1
- Milton Fischmann10