The Great Western Railway, also known as the GWR, was founded by Royal Assent on 31 August 1835. The idea of a railway from Bristol to London had first been mooted in 1824, and finally in 1833 a committee of four prominent Bristol businessmen, namely George Jones, John Harford, Thomas Richard Guppy and William Tothill, had joined together and provided impetus and capital for the project. It took two years to survey the line and push the necessary legislation through Parliament. The first train ran from Bristol to Bath on 31 August 1940, full services started in 1841 and in 1842 Swindon Locomotive Works started operation. The London terminus of the GWR was at Paddington station.

At its inception, the GWR had a board of 24 directors which was divided into two committees based in London and Bristol. The first chairman, who sat on the London committee, was Benjamin Shaw and the first deputy chairman was Robert Bright, a member of the Bristol committee. Sir Daniel Gooch was the first Locomotive Superintendent, a post that came later to be known as the Chief Mechanical Engineer. The GWR did not have the post of General Manager until 1863, when Charles Grierson was appointed. The first Secretary was Charles Saunders. Charles Russell became chairman in 1839. The GWR’s first Engineer (a post that would later be called the Chief Civil Engineer) was the renowned Isambard Kingdom Brunel, and he held the post from March 1835 to September 1859. The GWR was overseen by a Board of Directors.

At the turn of the century there were three departments under the General Manager. These were the General Department, New Works and Government Enquiries and Staff and Expenses. On the operational side of the GWR, the various different departments such as the Locomotive, Carriage and Superintendent, the Superintendent of the Line, the Goods Department and the Traffic Manager all used a similar administrative structure. These departments were headed by one manager and beneath this post responsibility was distributed into divisions based on geographical areas, which varied by department. The docks which were owned by the GWR were administrated separately from the railways under the control of the Chief Docks Manager. There were also facilitative administrative departments, as well as Hotels and Catering, Surveyor, Estate Agent, Stores departments and a Road Motor Engineer’s Department which operated the GWR’s road haulage service.

Brunel insisted on using a broad gauge track, which caused problems both in the civil engineering projects to build the railway and also during operation. A Gauge Commission had been appointed in 1846 and brought about the Gauge Act of 16 August 1846 which noted the systemic advantages of narrow gauge but did not compel the GWR to convert the full length of their track. From 1846 a standard gauge third rail was added to board gauge lines. From around 1868, led by then Chairman Sir Daniel Gooch, the GWR began to convert the entire system to standard gauge, and this was completed on 23 May 1892.

The main line of the Great Western Railway ran over the 118¼ miles between Bristol Temple Meads and Paddington station in London. The construction of the main line required several major engineering works. The chief among these was the two-mile long Box Tunnel between Bath and Chippenham. This challenging engineering work took around five years to complete, opening on 30 June 1841. Brunel also constructed viaducts and bridges, including the Maidenhead Bridge, opened on 1 July 1839 and the Royal Albert Bridge at Saltash which linked Devon and Cornwall across the River Tamar and which opened on 11 April 1859.

The GWR had a road haulage operation, which connected with its rail freight services. The GWR also owned and operated a number of docks and harbours, and after the Grouping in 1923 the GWR became the world’s largest dock-owning company. It wholly owned 16 docks, including Plymouth, Swansea and Cardiff, and jointly owned five other docks. The South Wales ports mainly handled minerals and food, whilst passenger ships used Plymouth and Fishguard. The GWR’s docks and harbours allowed goods and passengers to transfer between rail and sea with ease. The GWR also owned its own hotels, which numbered eight by 1923. The showpiece hotel was the Great Western Royal Hotel which was connected to Paddington station.

The Railways Act 1921 came into effect on 1 January 1923 and the multitude of smaller railway companies were consolidated in the Big Four. The GWR absorbed seven larger constituent companies as well as 26 smaller railways covering most of Wales, the Welsh Marches, Somerset, South Devon and Cornwall. It was third largest Big Four railway, with around 3,800 miles of track.

The Great Western Railway, along with all the other Big Four railway companies was nationalised and taken over by the Railway Executive, part of the British Transport Commission from 1 January 1948. The Western Region of British Railways took over responsibilty for GWR's sphere of operations.