Maupertuis Bay (French: Baie Maupertuis) is a bay in the Australian state of South Australia located on the south-west coastline of Kangaroo Island.

[1] It faces to the south-west and extends for a distance of about 13 kilometres (8.1 mi) from an unnamed headland in the north-west to Cape du Couedic in the south-east.

[1] Rivers draining into the bay includes the Rocky River which rises from within a catchment located in both the Flinders Chase National Park and the Ravine des Casoars Wilderness Protection Area.

[4] On 24 April 1899, the Scottish barque Loch Sloy was wrecked off the coast from Maupertuis Bay[5] resulting in the deaths of all but three of its 32 crew and passengers.

Since 2012, the waters of the bay have been located within a "habitat protection zone" with the Western Kangaroo Island Marine Park which is managed by the Government of South Australia.