Rosthwaite is a settlement in the Borrowdale parish of Cumberland, Cumbria, England. It is also in Borrowdale in the English Lake District to the south of Derwent Water. The B5289 road goes through the settlement and it is to the east of the Honister Pass.

Historically part of Cumberland, the nearest town to Rosthwaite is Keswick, which is situated approximately 6 miles (9.7 km) to the north.

Rosthwaite is host to many interesting post-glacial geographical features. The town nestles underneath the How, a large roche moutonnée, with a smaller roche moutonnée being further to the west.

Near to and within Rosthwaite is also a set of terminal moraines which show the staggered retreat of the Stonethwaite Glacier. These are quite obvious, with the middle and best preserved moraine being found NY 258145.

Rosthwaite is within the Copeland UK Parliamentary constituency. Trudy Harrison is the Member of Parliament.

Before Brexit for the European Parliament its residents voted to elect MEP's for the North West England constituency.

For Local Government purposes it is in the Keswick Ward of Cumberland Council.

Rosthwaite is parished; Borrowdale Parish Council.

• Listed buildings in Borrowdale