The Great Northern, Piccadilly and Brompton Railway (GNP&BR), also known as the Piccadilly tube, was a railway company established in 1902 that constructed a deep-level underground "tube" railway in London, England. The GNP&BR was formed through a merger of two older companies, the Brompton and Piccadilly Circus Railway (B&PCR) and the Great Northern and Strand Railway (GN&SR). It also incorporated part of a tube route planned by a third company, the District Railway (DR). The combined company was a subsidiary of the Underground Electric Railways Company of London (UERL).

The Metropolitan District Railway, also known as the District Railway, was a passenger railway that served London, England, from 1868 to 1933. Established in 1864 to complete an "inner circle" of lines connecting railway termini in London, the first part of the line opened using gas-lit wooden carriages hauled by steam locomotives. The Metropolitan Railway operated all services until the District Railway introduced its own trains in 1871. The railway was soon extended westwards through Earl's Court to Fulham, Richmond, Ealing and Hounslow. After completing the inner circle and reaching Whitechapel in 1884, it was extended to Upminster in Essex in 1902.