The Railway Executive Committee (REC) was a government body which controlled the operation of Britain's railways during World War I and World War II. It should not be confused with the Railway Executive which was a division of the British Transport Commission.

In both cases, this period of government control was followed by a major re-organisation of the railways.

The Railway Executive Committee (REC) was formed in 1912 to act as an intermediary between the War Office and the various British railway companies. It was formed in response to the Agadir Crisis for a contingency in which it would have to defend its Triple Entente partners France and Russia against a Triple Alliance offensive. The companies were already involved in the transport of many thousands of troops during annual manoeuvres and it was realised that better coordination and planning would be required if the United Kingdom were to enter into a future European war. In 1911, the companies began to plan for the movement of troops, horses and equipment to the embarkation ports, chiefly Southampton, in case of mobilisation; the main role of the REC was to oversee this work. When completed, the orders for this complicated plan that were issued to the various railways were known as the "War Book".

Using powers granted to the government by the Regulation of the Forces Act 1871, the REC took control of the national rail network on 4 August 1914, the day that war was declared and mobilisation began. Alexander Kaye Butterworth was appointed chairman. REC control lasted from 1914 to 1921. It was followed by the Railways Act 1921 which led to the creation of the Big Four British railway companies in 1923. Herbert Ashcombe Walker was acting chairman of the REC in January 1917.

The REC was re-formed on 24 September 1938 with a remit to run the British railways if war broke out. The railways would later be brought under government control through the REC under the direction of the Ministry of Transport.

The Big Four railway companies, comprising the Great Western Railway (GWR), the London, Midland and Scottish Railway (LMS), the London and North Eastern Railway (LNER), and the Southern Railway (SR), along with the London Passenger Transport Board (LPTB) were initially represented by Sir Ralph Wedgwood (chairman) for LNER, Sir James Milne (deputy chairman) for GWR, Sir William Wood for LMS, Gilbert Szlumper for SR, and Frank Pick for LTPB. The secretary of the committee was G. Cole Deacon from the Railway Companies' Association.

Initially, the role of the REC was advisory and coordinated the existing emergency plans and preparations of the railway companies and the Railway Technical Committee for such matters as civilian evacuation and air raid precautions.

At first, the offices of the REC were at Fielden House in Westminster. Unlike the railway companies, which were planning to move their headquarters out of London, the REC remained in London to stay in close contact with the government. The basement in Fielden House was unsuitable, so the unused Down Street tube station was converted into bomb-proof underground offices to become the headquarters of REC. The only available space was on the platforms, but Piccadilly Line trains still passed through the station. Under great secrecy, new walls were built at night when the trains had stopped running. The doors to the new headquarters were fitted with gas locks, and short, secret, platforms were added, where REC members and senior staff could stop a train and travel in the cab to the next station. The new headquarters included offices, dormitories (with space for 12 senior officials and 22 members of staff), kitchens, and mess rooms.