Publishers
- M. & J. Hobbs 4
- M. And J. Hobbs 1
- M. Carey & Sons 1
- M. Macdonald 1
- M. McGregor 1
- M. Moreau 1
- M.A. Donohue & Co. 1
- M.D. Jenkins 1
- M.D.E. Publications 1
- M.F. Feheley 2
- M.I.P.I. PUBLISHING 2
- M2 1
- Mac pennys 1
- Macdermott & Chant Ltd. 1
- MacDonald 22
- MacDonald & Co. 1
- Macdonald & Co. (Publishers) Ltd. 9
- Macdonald & Jane's (publishers) Ltd 1
- Macdonald and Jane's 10
- MacDonald Children's Books 1
- MacDonald Educational 1
- Macdonald Futura Publishers Ltd. 1
- Macdonald Orbis 1
- Macdonald Phoebus Limited 1
- Macdonald Purnell 1
- MacDonald Young Books 1
- MacGibbon & Kee 2
- Mackie & Co. Limited 2
- MacMillan 44
- Macmillan & Co. 30
- Macmillan & Co. Ltd. 137
- Macmillan And Bowes 1
- Macmillan Children's Books 28
- Macmillan London Limited 15
- MacMillan Press 1
- Macmillan Press Ltd 2
- MacMillan Publishers Ltd. 2
- Macmillan Publishing Co. 8
- Macmillan Publishing Co. Inc. 3
- Macmillan, New York 1
- Maeght Editeur 1
- Magdalen College 4
- Magna Books 2
- Magna Press 1
- Magnard 1
- Magpie Publishing 2
- Mainstream Publishing 5
- Mainstream Publishing Company (Edinburgh) Ltd. 1
- Mallard Press 1
- Malta Ornithological Society 1
- Mamelok Press 2
- Mammoth 4
- Manas Publications 2
- Manchester City Galleries 1
- Manchester University Press 7
- Mantle Oral History Project 1992 1
- Marcel Dekker 1
- Marcus Harris & Lewis Ltd. 5
- Marcus Ward & Co. 5
- Marcus Ward & Co. Limited 1
- Margaret Newton 1
- Margo 1
- Mariner Press 1
- Maritime Books 2
- Maritime Publications 1
- Marjory Lester 1
- Mark + Moody Limited 1
- Markosia Enterprises Ltd. 2
- Marks & Spencer 3
- Marlborough College 3
- Marshall Brothers 1
- Marshall Pickering 1
- Marshall, Morgan & Scott 1
- Marsilio 1
- Marston House 1
- Martin Bairstow 1
- Martin Holmes Rallying 2
- Martin Robertson 1
- Martin Secker 1
- Martin's Printing Works 1
- Martinus Nijhoff 2
- Marvel Comics Limited 1
- Marvel Entertainment Group 4
- Mascot Media 1
- Maskew Miller 1
- Massin Editeur 1
- Mastercraft Printing 1
- Mastiff Club Of America 1
- Matador 4
- Mathern Parochial Church Council 1
- Matrix Design 1
- Matthew S. Batham 1
- Matthiesen Fine Art 1
- Max Parrish 7
- Max Parrish And Co Ltd 2
- Max Reinhardt 4
- Mayflower Books 1
- Mayflower Publishing Company 1
- Mazzoleni 1
- Mbi Publishing 8