Cardigan Bay (Welsh: Bae Ceredigion or Bae Aberteifi) is a large inlet of the Irish Sea, indenting the west coast of Wales between the Llŷn and Pembrokeshire peninsulas.
Cardigan Bay has white-sand beaches, soft turquoise sea and a unique marine life (such as dolphins), making it one of the finest stretches of coastline in the UK.
Much of the coast surrounding the bay is fertile farmland, dotted with towns and seaside resorts such as Fishguard, New Quay, Aberaeron, Aberystwyth, Aberdyfi, Barmouth and Pwllheli on the Cambrian Coast. Major rivers flowing into the bay include the Teifi, Rheidol, Dyfi, Aeron, and Mawddach.
Up until the early twentieth century it supported a strong maritime industry. Cardigan at the mouth of the Teifi was at one time a more important port than Cardiff.
The central and northern area of the Bay is the location of the legendary Cantre'r Gwaelod, the Lowland Hundred or Hundred under the Sea. The song Bells of Aberdyfi is based on this drowned world.