Janet's Foss is a small waterfall close to the village of Malham, North Yorkshire.
The waterfall is fed by Gordale Beck, which falls over a limestone outcrop into a deep pool in Wedber Wood.. The pool was traditionally used for sheep dipping.
The name Janet occasionally called Jennet, is believed to refer to a fairy queen supposed to inhabit a cave at the rear of the fall. Foss is a Nordic word for waterfall, still used in Scandinavia.
Janet's Foss was the location of the fictional Molkham Falls featured in the 2006 independent British film, Waterfall.
Janet's Foss is occasionally used by all-weather wild swimmers.