Watendlath Beck is the stream that drains Watendlath Tarn, high in a hanging valley between the Borrowdale and Thirlmere valleys in the Lake District, Cumbria.

Fed ultimately by Bleatarn Gill from Blea Tarn above, the beck descends from the tarn at around 863 feet (263 m) above sea level and flows down toward Derwent Water, feeding the celebrated Lodore Falls along the way.

A waterfall on Watendlath Beck forms the centrepiece of a popular 3. 9-mile (6. 2 km) loop trail from Derwent Water, offering elevated views over the lake. The route is well regarded by walkers and rated highly for its scenic quality.

An old packhorse bridge spans the beck at the hamlet of Watendlath, adding a historic character to the surrounding landscape, which is owned and managed by the National Trust.