British Railways (BR), which from 1965 traded as British Rail, was a state-owned company that operated most of the overground rail transport in Great Britain from 1948 to 1997. It was formed from the nationalisation of the Big Four British railway companies, and was privatised in stages between 1994 and 1997. Originally a trading brand of the Railway Executive of the British Transport Commission, it became an independent statutory corporation in January 1963, when it was formally renamed the British Railways Board.

The period of nationalisation saw sweeping changes in the railway. A process of dieselisation and electrification took place, and by 1968 steam locomotives had been entirely replaced by diesel and electric traction, except for the Vale of Rheidol Railway (a narrow-gauge tourist line). Passengers replaced freight as the main source of business, and one third of the network was closed by the Beeching cuts of the 1960s in an effort to reduce rail subsidies.

On privatisation, responsibility for track, signalling and stations was transferred to Railtrack (which was later brought under public control as Network Rail) and that for trains to the train operating companies.

The British Rail Double Arrow logo was formed of two interlocked arrows showing the direction of travel on a double track railway and was nicknamed "the arrow of indecision". It is now employed as a generic symbol on street signs in Great Britain denoting railway stations, and is still printed on railway tickets as part of the Rail Delivery Group's jointly managed National Rail brand.