Publishers
- M-Sport Ltd 1
- M. & J. Hobbs 5
- M. A. Donohue & Co. 1
- M. And J. Hobbs 1
- M. Carey & Sons 1
- M. Macdonald 1
- M. McGregor 1
- M. Moreau 1
- M.A. Donohue & Co. 2
- M.A. Pittman 1
- M.D. Jenkins 1
- M.D.E. Publications 1
- M.F. Feheley 2
- M.I.P.I. PUBLISHING 2
- M.I.T. Press 1
- M2 1
- Mac pennys 1
- Macdermott & Chant Ltd. 1
- MacDonald 21
- MacDonald & Co. 3
- Macdonald & Co. (Publishers) Ltd. 10
- Macdonald & Jane's (publishers) Ltd 1
- Macdonald and Jane's 11
- 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 50
- Macmillan & Co. 32
- Macmillan & Co. Ltd. 167
- Macmillan And Bowes 1
- Macmillan Children's Books 38
- Macmillan Journals Ltd 1
- Macmillan London Limited 17
- MacMillan Press 1
- Macmillan Press Ltd 2
- MacMillan Publishers Ltd. 2
- Macmillan Publishing Co. 9
- Macmillan Publishing Co. Inc. 1
- Macmillan, New York 1
- Macy-Masius 1
- Maeght Editeur 1
- Magdalen College 4
- Magna Books 2
- Magnard 1
- Magnes Press 1
- Magpie Publishing 2
- Mainstream Publishing 10
- 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 6
- Mantle Oral History Project 1992 1
- Marcel Dekker 1
- Marcus Harris & Lewis Ltd. 5
- Marcus Ward & Co. 6
- Marcus Ward & Co. Limited 2
- Margaret Newton 1
- Margo 1
- Mariner Press 1
- Maritime Books 3
- Maritime Publications 1
- Mark + Moody Limited 1
- Markosia Enterprises Ltd. 2
- Marks & Spencer 3
- Marks and Spencer Limited 1
- Marlborough College 3
- Marsh Brothers & Co. Limited 1
- Marshall Brothers 1
- Marshall Harris & Baldwin Ltd. 2
- Marshall Pickering 1
- Marshall, Morgan & Scott 1
- Marsilio 1
- Marston House 1
- Martin Bairstow 1
- Martin Holmes Rallying 3
- Martin Robertson 1
- Martin Secker 1
- Martin's Printing Works 1
- Martinus Nijhoff 2
- Marvel Comics Limited 1
- Marvel Entertainment Group 1
- Mascot Media 1
- Maskew Miller 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