Malham Tarn is a glacial lake near the village of Malham in the Yorkshire Dales, England. The lake is one of only eight upland alkaline lakes in Europe. At an altitude of 377 m above sea level it is the highest marl lake in the United Kingdom.
The primary outflow is a small stream at the southern end of the lake. The outflow stream goes underground after approximately 500 m before emerging downstream of Malham Cove as a source of the River Aire.
