The Joint Committee of Light Metal Trades Unions (LMTU) was a trade union committee consisting of unions based in the United Kingdom with members involved in producing castings for industry and construction.

The committee was established in 1911,^[2] as the Joint Committee of the Light Castings Trade Unions, adopting its final name in about 1930.^[3] It negotiated with the National Metal Trades Federation, which represented companies which produced castings.^[4]

The committee was based in Rotherham, sharing its offices and general secretary with the National Union of Domestic Appliance and General Metal Workers.^[1]

By the 1980s, the committee had the following members:^[1]

• Amalgamated Society of Boilermakers, Shipwrights, Blacksmiths and Structural Workers
• Amalgamated Union of Engineering Workers (Engineering, Foundry and TASS sections)
• Association of Patternmakers and Allied Craftsmen
• Association of Professional, Executive, Clerical and Computer Staff
• National Union of Domestic Appliance and General Metal Workers
• National Union of Sheet Metal Workers, Coppersmiths and Heating and Domestic Engineers
• Transport and General Workers' Union (Vehicle Building Automotive Group)