Bristol Channel, inlet of the Atlantic Ocean, c.85 mi (140 km) long and from 5 to 50 mi (8.1–80 km) wide, stretching westward from the mouth of the River Severn and separating Wales from SW England. Its chief bays are Carmarthen and Swansea in Wales and Barnstaple (or Bideford) and Bridgwater in England. Many cities are on or near the channel; among the largest are Bristol, Newport, Cardiff, and Swansea. Along the coast of S Wales is a great concentration of economic activity, and Bristol Channel serves as a major shipping corridor. Milford Haven, a major oil-importing center, has a harbor that can accommodate large modern tankers.