| Alcock Tarn | |
|---|---|
Location within Cumbria | |
| Location | Cumbria, England |
| Coordinates | 54°27′44″N 3°0′20″W / 54.46222°N 3.00556°W |
| Type | Lake |

Alcock Tarn is a lake in Westmorland and Furness, Cumbria, England. It is located high in the fells on Heron Pike, roughly a mile and a half east of Grasmere.
Alcock Tarn was originally known as Butter Crags Tarn and was enlarged by means of a stone and earth dam in the 19th century to a depth of about 6 ft (1.8 m). The owner, a Mr Alcock of Grasmere, then stocked it with brown trout.