Trade unions
M
| Full Name | Short Name | Notes |
|---|---|---|
| Machine and General Labourers' Union | MGLU | |
| Manufacturing Science and Finance | MSF | |
| Marine Workers' Union | MWU | |
| Medical Practitioners Union | MPU | |
| Merchant Seamen's League | MSL | |
| Midland Counties Miners' Federation | MCMF | Formed in 1886. In 1945, became the Midland Area of the National Union of Mineworkers. Dissolved in 2011. |
| Midland Textile Association | MTA | |
| Miners' Federation of Great Britain | MFGB | Formed 1889. Later renamed the National Union of Mineworkers in 1945. |
| Musicians' Union | MU |