The British Transport Commission (BTC) was created by Clement Attlee's post-war Labour government as a part of its nationalisation programme, to oversee railways, canals and road freight transport in Great Britain (Northern Ireland had the separate Ulster Transport Authority). Its general duty under the Transport Act 1947 was to provide an efficient, adequate, economical and properly integrated system of public inland transport and port facilities within Great Britain for passengers and goods, excluding transport by air.

The BTC came into operation on 1 January 1948. Its first chairman was Lord Hurcomb, with Miles Beevor as Chief Secretary. Its main holdings were the networks and assets of the Big Four national regional railway companies: the Great Western Railway, London and North Eastern Railway, London, Midland and Scottish Railway and the Southern Railway. It also took over 55 other railway undertakings, 19 canal undertakings and 246 road haulage firms, as well as the work of the London Passenger Transport Board, which was already publicly owned. The nationalisation package also included the fleets of 'private owner wagons', which industrial concerns had used to transport goods on the railway networks.