The National Society of Metal Mechanics (NSMM) was a trade union in the United Kingdom which existed between 1872 and 1985.

The organisation was founded in Birmingham in 1872 as the Amalgamated Brassworkers Society.

Led for many years by William John Davis, it was soon renamed the National Society of Amalgamated Brassworkers.

[3] In 1919, members rejected a proposal to join the Amalgamated Society of Engineers, and instead chose to expand the union's remit, renaming the body as the National Society of Brass and Metal Mechanics.

[5] In 1985, the union merged with the Technical, Administrative and Supervisory Section; at this point, its membership was 27,000.