Wigtown Bay is a large inlet of the Irish Sea on the coast of Galloway in southwest Scotland.
Its coastline falls entirely within the modern administrative area of Dumfries and Galloway and shared between the historical counties of Wigtownshire and Kirkcudbrightshire.
The bay is broadly triangular in form, widening to the southeast and with the estuary of the River Cree entering from the northwest at its head.
The inner parts of the bay are characterized by large expanses of salt marsh and mudflats.
A proposal to construct an offshore windfarm in Wigtown Bay was turned down by the Scottish government in early 2011.