The British Rail Class 373 or TGV TMST train is an electric multiple unit that operates Eurostar's high-speed rail service between Great Britain, France and Belgium via the Channel Tunnel. Part of the TGV family, it has a smaller cross-section to fit within the constrictive loading gauge in Great Britain, was originally able to operate on the UK third rail network, and has extensive fireproofing in case of fire in the tunnel. This is both the longest—387 metres (1,270 ft)—and fastest train in regular UK passenger service.
Known as the TransManche Super Train (Cross-channel Super Train) during development up until start of service in 1993, the train is designated Class 373 under the British TOPS classification system and as series 373000 TGV in France. It was built by GEC-Alsthom (now Alstom) at its sites in La Rochelle (France), Belfort (France) and Washwood Heath (UK) and by Brugeoise et Nivelles (BN, now part