Publishers
- Marrin Publishing 1
- Marshall Brothers 1
- Marshall Cavendish Children's Books Limited 1
- Marshall Harris & Baldwin Ltd. 2
- Marsilio 1
- Martin Bairstow 3
- Martin Robertson 1
- Martin Secker 2
- Martin's Printing Works 1
- Martinus Nijhoff 3
- Marvel Comics Limited 2
- Marvel Entertainment Group 1
- Maskew Miller 1
- Massey University Press 1
- Mastercraft Printing 1
- Mastiff Club Of America 1
- Matador 3
- Matilda And War Memorial Hospital 1
- Matthaus Publishers 1
- Matthew S. Batham 1
- Matthiesen Fine Art 1
- Max Parrish 6
- Max Parrish And Co Ltd 2
- Max Reinhardt 3
- Maxiprint 2
- Mayflower Books 1
- Mazzoleni 1
- Mbi Publishing 9
- McClanahan Book Company Inc. 1
- McClelland and Stewart Limited 2
- McClure, Phillips & Co. 1
- McCorquodale & Co. 3
- McCorquodale & Co. Ltd. 2
- McDonald Institute For Archaeological Research 1
- McDougall's Educational Co. Ltd. 1
- McFarland & Company, Inc. 3
- McFarlane & Erskine 1
- McGill-Queen's University Press 1
- McGraw-Hill 8
- McGraw-Hill Book Company 13
- Mcgraw-Hill Publishing Company Ltd. 3
- McGraw-Hill Ryerson Limited 1
- McLoughlin Bros. 5
- McService 1
- Mechanical Engineering Publications Limited 4
- Mecredy, Percy & Co. Ltd. 1
- Medallion Press Limited 1
- Meissner & Buch 1
- Meline, Cans Et Compagine 1
- Melrose Books 1
- Melrose Press Ltd. 1
- Menoshire 1
- Mercat Press 1
- Mercatorfonds 1
- Mercer University Press 2
- Mercia Books 1
- Mercian Manuals Ltd 2
- Mercier Press 1
- Mercury Books 2
- Meresborough Books 1
- Meridian Publications 1
- Meridian Publishing Co. 1
- Merlin Books Ltd. 3
- Merlin Bookshop 2
- Merlin Unwin Books 4
- Merrell Holberton Publishers 1
- Merrell Publishers Limited 4
- Merrimack Publishing Corp. 2
- Merthyr Tydfil and District Naturalists' Society 3
- Merthyr Tydfil Historical Society 3
- Merton Priory Press 2
- Messrs. Stooke And Son 12
- Methuen 11
- Methuen & Co. 4
- Methuen & Co. Ltd. 127
- Methuen Children's Books 30
- Methuen Children's Books Ltd. 11
- Methuen London Ltd 1
- Methuen Walker Books 2
- Metzler & Co. 1
- Michael D. Dobson 1
- Michael Hale 1
- Michael Hardcastle Publications 1
- Michael Imhof Verlag Gmbh & Co. 1
- Michael J. Elsden 1
- Michael Joseph 31
- Michael Joseph Ltd 1
- Michael Moon 2
- Michael Neugebauer Ltd 1
- Michael O'Mara books Limited 3
- Michael Russell 1
- Michael Russell (publishing) Ltd 2
- Michael Stanfield Holdings 3
- Michael Stanfield Holdings Ltd. 2
- Mid Glamorgan County Libraries 1
- Middleton Press 10
- Midland 1
- Midland Automobile Club 3
- Midland Bank 1
- Midland Counties Publications 4