Loch Lomond and The Trossachs National Park (Scottish Gaelic: Pàirc Nàiseanta Loch Laomainn is nan Tròisichean) is a national park in Scotland centred on Loch Lomond and the hills and glens of the Trossachs, along with several other ranges of hills. It was the first of the two national parks established by the Scottish Parliament in 2002, the second being the Cairngorms National Park. The park extends to cover much of the western part of the southern highlands, lying to the north of the Glasgow conurbation, and contains many mountains and lochs. It is the fourth-largest national park in the British Isles, with a total area of 1,865 km (720 sq mi) and a boundary of some 350 km (220 mi) in length. It features 21 Munros (including Ben Lomond, Ben Lui, Beinn Challuim, Ben More and two peaks called Ben Vorlich) and 20 Corbetts.
The park straddles the Highland Boundary Fault, which divides it into two distinct regions - lowland and highland - that differ in underlying geology, soil types and topography. The change in rock type can most clearly be seen at Loch Lomond itself, as the fault runs across the islands of Inchmurrin, Creinch, Torrinch and Inchcailloch and over the ridge of Conic Hill. To the south lie green fields and cultivated land; to the north, mountains.