| Label | Founded | Label type | Label code (LC) |
|---|---|---|---|
| Magnet | 1973 | Production | 3389 |
| Majestic Rock | 2003 | Bootleg Production | — |
| Major Minor | 1966 | Original Production | — |
| Mango Records | — | Distributor | 407 |
| Manifesto | — | Original Production | — |
| Manticore | 1973 | — | 3042 |
| Mantra Recordings | 1995 | Original Production | 11591 |
| Marks & Spencer | 1884 | Distributor | — |
| Marshall Cavendish Partworks Limited | 5 July 1982 | Publisher | — |
| Marshall Records | 2016 | — | — |
| Med School | 2006 | Imprint | 12939 |
| Mega Dodo | 11 May 2011 | Original Production | — |
| Memphis Industries | 1998 | Original Production | 13549 |
| Mercury KX | February 2017 | Imprint | 171 |
| Meridian Records | 1977 | — | — |
| Metal & Dust | — | Imprint | — |
| Metalheadz | 1994 | Original Production | — |
| Metro | — | Imprint | — |
| Metro Doubles | — | Imprint | — |
| Mighty Force | 1991 | Original Production | — |
| Millennium Jazz Music | 2003 | Original Production | — |
| Ministry of Sound | 1993 | — | 11683 |
| Mixmag | — | Original Production | — |
| Mixtape Madness | September 2010 | Production | — |
| Mo Wax | 1992 | Original Production | — |
| Mo' Wax | 1 January 1992 | — | privately held company |
| Modena Records | 28 February 1997 | Original Production | — |
| Modern Love | 2002 | Original Production | — |
| Modern Urban Jazz | 1995 | Publisher | — |
| Mojo | — | Production | — |
| Moshi Moshi Records | 1998 | Original Production | 23175 |
| Mote-Evolver | 2006 | Original Production | — |
| Mother Records | — | Original Production | 309 |
| Movie Queen Music | 1 June 2012 | Original Production | — |
| Moving Shadow | 1991 | Original Production | 5681 |
| MPL Communications | 1 January 1970 | — | private company limited by shares |
| Mr Bongo | 1989 | Original Production | 12527 |
| MTA Records | 2009 | Original Production | — |
| Mumble Etc. | 2013 | Original Production | — |
| Music De Wolfe | 1909 | Original Production | — |
| Music for Nations | 1983 | Original Production | 8541 |
| Mute | 1978 | Imprint | 5834 |