Guichen Bay, (French: Baie de Guichen) is a bay located on the south-east coast of South Australia about northwest of Mount Gambier and about south-southeast of Adelaide. It was named in 1802 by the Baudin expedition of 1800-03 after Luc Urbain de Bouëxic, comte de Guichen. The town of Robe is located at the southern end of the bay.