The Baie de Douarnenez (French pronunciation: [bɛ də dwaʁnəne]; Breton: Bae Douarnenez) is a bay in Finistère, France, between the Crozon Peninsula to the north and the Cap Sizun to the south.
Although half closed off to the west by Cap de la Chèvre, it opens out again to a width of 9 kilometres (5.6 mi; 4.9 nmi) on the side of the Mer d'Iroise.
To the south-east is the port of Douarnenez, which was the center of a large sardine industry in the early 20th century.
The bathing station at Morgat is located to the north, on the Crozon peninsula.
The mythical town of Ys, which legend says was engulfed by the ocean, is commonly said to be located in this bay.