The GMB was founded on 31 March 1889 in Canning Town, East London by Will Thorne who became its first General Secretary.

The first campaign on behalf of its members was to end the slavery of 12 and 18 hour shifts, 7 days a week. The fledgling union campaigned for an 8 hour day and six day week. It was successful and resulted in the first working time agreement anywhere in the world.

In modern times, recent legislation has confirmed this success by introducing the Working Time Directive, limiting the hours of work to 48 a week.

Since 1924 the union has undergone many amalgamations with other unions, including the Boilermakers Union.