The Trossachs (listen^ⓘ; Scottish Gaelic: Na Tròiseachan) generally refers to an area of wooded glens, braes, and lochs lying to the east of Ben Lomond in the Stirling council area of Scotland. The name is taken from that of a small woodland glen that lies at the centre of the area, but is now generally applied to the wider region.

The wooded hills and lochs of the area may be considered to represent a microcosm of a typical highland landscape, and the woodlands are an important habitat for many species. Much of the Trossachs area is protected by various different conservation designations, including the Great Trossachs Forest National Nature Reserve.

The Trossachs form part of the Loch Lomond and The Trossachs National Park, which was established in 2002. The area has long been visited by tourists due to the relative proximity of major population centres such as Glasgow and Stirling, and remains popular with walkers, cyclists and tourists. Scenic boat rides on Loch Katrine are popular with visitors: the steamer SS Sir Walter Scott, launched in 1899, remains in operation. The Great Trossachs Path, one of Scotland's Great Trails, is a 48 km route suitable for walkers, cyclists and horse riders. It runs between Callander in the east and Inversnaid on the banks of Loch Lomond in the west, passing along the northern shores of Loch Katrine and Loch Arklet.

The name Trossachs involves the Brittonic root trōs meaning "across" (cf. Welsh traws), perhaps conserving the compound trawsfynydd meaning "cross-hill".

Also suggested is a derivation from a Gaelic word for "bristly".

The Trossachs glen lies between Ben A'an to the north and Ben Venue to the south, with Loch Katrine to the west and Loch Achray to the east. It lies at the centre of the wider region, which is generally regarded as being bounded by Glen Gyle to the south, with the western boundary being the road between Stronachlachar and Aberfoyle.^{[dubious – discuss]} Loch Doine, Loch Voil, and Loch Lubnaig form the northern and eastern boundary of the area.

The A821 road between Aberfoyle and Callander runs through this glen, and is the main access route into the Trossachs from the south and east. The section between Aberfoyle and the Trossachs glen runs through the Achray Forest, reaching a height of 238 m above sea level at the summit of the Duke's Pass. The main route to Callander continues east via the north shores of Loch Achray and Loch Venachar, whilst a branch of the A821 heads west to finish at the western end of Loch Katrine. No public road continues along the shore of Loch Katrine, although the Great Trossachs Path allows walkers and cyclists to follow the northern shore round to Stronachlachar on the western shore. From here a minor road heads west to Loch Lomond. Stronachlachar can also be reached by the B829 road from Aberfoyle, which passes north of Loch Choin and Loch Ard.

The small town of Callander and the village of Aberfoyle lie at the edge of the Trossachs, however Brig o' Turk is the only settlement of any size within the Trossachs. The Lake of Menteith, situated near Aberfoyle, lies about six miles (10 km) to the south east of the glen, on the edge of the Trossachs area. The lake is a fishing destination that features the ruins of Inchmahome Priory on one of its islands, Inchmahome, where Mary, Queen of Scots was taken as a child before being taken to France for her protection.