Loch Tummel (Scottish Gaelic: Loch Teimheil) is a long, narrow loch, 7 km (4.3 mi) north west of Pitlochry in the council area of Perth and Kinross, Scotland. It is fed and drained by the River Tummel, which flows into the River Tay about 13 km (8.1 mi) south-east of the Clunie Dam at the loch's eastern end.

The loch is traversed by roads to both north and south. Along the northern side the road is numbered as the B8019, and runs from the Pass of Killiecrankie on the A9 in the east to Tummel Bridge at the head of the loch. The road on the southern side is unclassified, and meets the A9 further south, near to Pitlochry.

The loch gives its name to the Loch Tummel National Scenic Area (NSA), one of 40 such areas in Scotland, which are defined so as to identify areas of exceptional scenery and to ensure its protection by restricting certain forms of development. The Loch Tummel Lyon NSA covers 9,013 ha (22,272 acres), all of which lies within Perth and Kinross. The NSA covers the hills surrounding the loch, and extends along the River Tummel to also take in the area surrounding the Pass of Killiecrankie on the River Garry.