Buttermere is a lake in Lake District, a national park in the county of Cumbria in the North West of England. Originally the lake was in Cumberland. Buttermere is located southeast of the Crummock Water and Loweswater lakes. The nearby village of Buttermere takes its name from the lake. It is owned by the National Trust.
There is a 7.2 km hiking trail around the lake that at one point leads the hiker through a tunnel through rocks. Borrowdale is reached via the southern Honister Pass.
There are two possible explanations for the name Buttermere. The first is that the name would refer to the fertile pastures on the alluvial plains on both sides of the butter lake to the Old English word butere. The second explanation is a distortion of the Old Norse proper noun Buthar. In any case, it is consistent with the local tradition that Buttermere was once owned by an 11th-century Norwegian leader Buthar. Large numbers of Vikings settled in Cumbria during the 9th and 10th centuries. Many names in the region are of Norwegian origin: rivers are called becks after the Old Norse bekkr; mountains are fells of fjall; waterfalls are forces of fos; ravines are gills; valleys are dales of dalr; and small lakes are called tarns, derived from tjorn which means tear.