The Severn Tunnel is a railway tunnel in the United Kingdom, linking South Gloucestershire in the west of England to Monmouthshire in south Wales under the estuary of the River Severn. It was constructed by the Great Western Railway (GWR) between 1873 and 1886 for the purpose of dramatically shortening the journey times of their trains, passenger and goods alike, between South Wales and Western England. It has often been regarded as the crowning achievement of GWR's chief engineer Sir John Hawkshaw.

South Gloucestershire is a unitary authority area in the ceremonial county of Gloucestershire, South West England. Towns in the area include Yate, Chipping Sodbury, Kingswood, Thornbury, Filton, Patchway and Bradley Stoke. The southern part of its area falls within the Greater Bristol urban area surrounding the city of Bristol.