The Galloway Hills are part of the Southern Uplands of Scotland, and form the northern boundary of western Galloway. They lie within the bounds of the Galloway Forest Park, an area of some 300 square miles (800 km²) of largely uninhabited wild land, managed by Forestry and Land Scotland. The unusual place names reflect a mixture of the Old Norse and Scottish Gaelic languages and hint at the range of influences which have acted on society within the area over the centuries.

The location of Galloway has been described as follows, "Galloway is contained by sea to the west (North Channel) and south (Solway Firth), the "Galloway Hills" to the north, and the River Nith to the east". So if we were to say "The hills of Galloway" we would be including all the hills within this area; but as the first sentence implies, the "Galloway Hills" is usually taken to mean a collection of ranges which lie mainly south of Loch Doon and which are not constrained by political boundaries. The boundary between Dumfries and Galloway Region and Ayrshire runs west to east over Kirriereoch hill, drops south of Mullwharchar to the shores of Loch Enoch, before heading northwards up the east shore of Loch Doon, and so runs more or less through what might well be considered the heart of the Galloway hills – around Loch Enoch.

The northern limit of this hill area is around the small towns of Dalmellington and Straiton, both in Ayrshire. The B741 runs on an east–west line between these two towns on its way to the town of Girvan on the Firth of Clyde. The B741 could therefore be taken as the northern limit of the Galloway Hills area.

From Straiton a minor road runs south by Stinchar Bridge through the northwest corner of these hills to meet another minor road which runs from Glentrool village northwards towards Girvan and Maybole. This latter road forms the western boundary of the Galloway Hills. It follows the valley of Water of Minnoch and for most of its length it passes through the extensive forestry plantations which lie to the west of the hills.

The A713 (Castle Douglas to Ayr road) forms the eastern boundary of these hills. As it heads south from Dalmellington it passes through the valley known as the Glenkens which separates the Galloway Hills from the Carsphairn and Scaur Hills hills to the east. There is an extensive hydro-electric scheme (commissioned 1935/36) with several dams and power stations that runs down through the Glenkens to end at Tongland Power Station near Kirkcudbright.

The A713 passes through Carsphairn on the Water of Deuch and St John's Town of Dalry on Water of Ken and also close to New Galloway at Kenbridge, at the northern end of Loch Ken. From New Galloway the A712 passes through the hills to Newton Stewart. This road passes Clatteringshaws Reservoir, the Queen's Way, Dunkitterick Cottage (the birthplace of Alexander Murray), a deer range, a wild goat park and Murray's Monument.

For most users of these hills, "the Galloway Hills" would mean the ranges which lie north of a line running eastwards along the north shores of Loch Trool, Loch Dee and Clatteringshaws Reservoir. This for them would be the notional true heartland of the Galloway Hills. The Southern Upland Way and the National Cycle Network Route Number Seven travel along this line. A slightly looser use of the phrase Galloway Hills would include the ranges which lie to the south of that line.

To the south of the A712, east of Clatteringshaws Reservoir is a hill called Cairnsmore of Dee or Black Craig of Dee (493 metres) which offers excellent views from the top over Clatteringshaws into the heart of the Galloway Hills. To the south of Murray's Monument is a range of hills around Cairnsmore of Fleet. The top of Cairnsmore of Fleet is over 2 km in length running almost north–south and it has tops at either end. To the south of this again is a group of small coastal hills around Cairnharrow just to the west of Gatehouse of Fleet. Immediately beyond that is the A75 road running close to the shore of the Solway Firth.