Bideford Bay, also known as Barnstaple Bay and often shown on maps as Barnstaple or Bideford Bay, is a large area of water on the northwest coast of Devon in South West England, at the southwestern end of the Bristol Channel where it joins the Celtic Sea. The bay extends from Hartland Point in the southwest to Morte Point in the northeast, a distance of , and is partly sheltered by the island of Lundy, offshore. It takes its alternative names from the towns of Bideford and Barnstaple, located respectively on the rivers Torridge and Taw which flow into the bay. The alternative spelling Barnstable Bay, in use long after that spelling became obsolete for the town, is also sometimes seen.