Publishers
- Meridian Publications 1
- Meridian Publishing Co. 1
- Merlin Books Ltd. 4
- Merlin Bookshop 2
- Merlin Unwin Books 7
- Merrell Publishers Limited 3
- Merrimack Publishing Corp. 1
- Merthyr Tydfil and District Naturalists' Society 1
- Merthyr Tydfil Historical Society 3
- Merton Priory Press 4
- Messrs. Stooke And Son 9
- Methuen 15
- Methuen & Co. 4
- Methuen & Co. Ltd. 109
- Methuen Children's Books 24
- Methuen Children's Books Ltd. 4
- Methuen London Ltd 3
- Methuen Walker Books 2
- Metzler & Co. 1
- Michael Hale 1
- Michael Hardcastle Publications 1
- Michael Imhof Verlag Gmbh & Co. 1
- Michael J. Elsden 1
- Michael Joseph 26
- Michael Joseph Ltd 3
- Michael Moon 2
- Michael O'Mara books Limited 3
- Michael Russell 2
- Michael Russell (publishing) Ltd 2
- Michael Sedgwick Memorial Trust 1
- Michael Stanfield Holdings 1
- Michael Stanfield Holdings Ltd. 1
- Middleton Press 8
- Midland 3
- Midland Automobile Club 2
- Midland Counties Publications 1
- Midland Educational Co. Ltd. 1
- Midland Publishing 19
- Midway 1
- Miklo 12
- Milepost 1
- Military Book Society 1
- Military Heritage Press 1
- Miller's 1
- Mills & Boon 2
- Millstream Books 2
- Millwheel Art Press 1
- Milner And Sowerby 1
- Ministry Of Agriculture Of The Republic Of Iraq 1
- Ministry Of Trade And Industry 1
- Miracle 1
- Miss N. Littleton 1
- Missionsbuchhandlung 1
- Missouri Bureau Of Geology And Mines 1
- Mitchell Beazley 6
- Mitchell Hughes and Clarke 6
- Mitchell Information Services Inc. 1
- Mitsubishi Motors Corporation 1
- Mixing 1
- Model Aeronautical Press Limited 1
- Model And Allied Publications 3
- Modern Promotions 3
- Mondo 1
- Monmouthshire Antiquarian Association 1
- Monnow Press 3
- Moody Press 1
- Moonglow Publishing 1
- Moonraker Press 2
- Moorland Publishing 7
- Morgan & Lester Publishers 1
- Morgan County Historical Society 1
- Morning Sun Books, Inc. 1
- Morris & Company 1
- Morris Motors Limited 2
- Morrison & Gibb Ltd. 4
- Moss Rose Press 32
- Mostra Mondiale Malacologia 1
- Motivate Publishing 2
- Motor Racing Publications Ltd. 22
- Motoraces Book Club 4
- Motorbooks 1
- Motorbooks International 11
- Motorbuch Verlag 3
- Mountain House 1
- Mountain Press Publishing Company 1
- Mouton De Gruyter 1
- Mr. Edwin Stooke 1
- Mr. Norman Rose 1
- Mrp 1
- MRP Publishing Ltd 1
- Mrs. Eugenia Stanhope 1
- Muinck & Co. 2
- Mulder & Zoon 4
- Mullet Press 1
- Mullock & Sons Limited 1
- Munksgaard 1
- Munshiram Manoharlal 1
- Murfett Pty. Ltd. 1
- Murray's Children's Books 4
- Murrays Sales & Service Co. 6