British Thomson-Houston (BTH) was a British engineering and heavy industrial company, based at Rugby, Warwickshire, England and founded as a subsidiary of the General Electric Company (GE) of Schenectady, New York, USA. They were known primarily for their electrical systems and steam turbines. BTH was taken into British ownership and amalgamated with the similar Metropolitan-Vickers company in 1928 to form Associated Electrical Industries (AEI), but the two brand identities were maintained until 1960. The holding company, Associated Electrical Industries (AEI), later merged with GEC, the remnants of which exist today as Marconi Corporation.
In the 1960s BTH apprenticeships were highly thought-of, with apprentices exposed to production of a wide range of industrial products. Each year in Rugby there was a big parade of floats run by its apprentices, many of whom lodged in the nearby Coton House apprentice hostel.
In 1980, G.E.C. Turbine Generators Ltd, on the Rugby site, was awarded a Queen's Awards for Enterprise.
During post-World War II Britain, AEI established a consolidated research effort at Aldermaston in Berkshire, England. The research centre was based at Aldermaston Court a large stately home owned by AEI that had been requisitioned for military use in the war era.
One of the BTH-built batch of New Zealand Railways DSC class Bo-Bo shunters has been preserved and is used in industrial service, complete with original Rolls-Royce engines. The locomotive (DSC406) is the primary motive power at Alliance Ltd, Pukeuri, New Zealand. All the others were scrapped between 1986 and 1990.