Peskowesk Lake is a large backcountry lake within Kejimkujik National Park and National Historic Site in Nova Scotia, situated at approximately 44°19′N 65°16′W. It forms the centerpiece of the Peskowesk Lake System, a roughly 48-kilometre canoe route that sees fewer visitors than other areas of the park due to the longer portages required to reach it. The lake is oriented with the prevailing winds, which has a practical implication for paddlers: a headwind when travelling deeper into the park typically signals fair weather, while a headwind on the return journey often precedes rain. Mid-day winds on Peskowesk can be stiff, and paddlers should anticipate the possibility of significant wave action, particularly in the afternoon.

The lake is accessible via several portages. Portage D connects it from Cobrielle Lake, while Portage J (1.2 km, following the Liberty Lake Trail for part of its length, with canoe rests provided) arrives from Back Lake and takes approximately 30 minutes to complete. Portage G (800 m) leads east from Peskowesk into Hitchemakaar Lake, with Portage H (200 m) continuing to Lower Silver Lake. From the western end, Portage K (400 m) involves a steep climb from the lake's shore and leads to Beaverskin Lake, while Portage N (760 m) is a two-part carry that passes near Poison Ivy Falls and a large glacial erratic before reaching Peskawa Lake. The start of Portage N can be difficult to locate, as Poison Ivy Falls has deposited a maze of granite boulders at the lake's edge. Portage F provides an exit toward Minards Bay and the Mersey River system.

Several backcountry campsites are located on or near the lake. Sites 31, 32, and 34 are on the eastern half of Peskowesk, and site 29 is also accessible on the lake. Île de l'Orignal, an island within the lake, hosts site 32. A small unnamed island with flat rock surfaces has been noted as a practical lunch stop, offering easy water access for filtering. The landscape in this part of Keji features windswept stands of red and white pine reminiscent of the Canadian Shield.

All visitors to Kejimkujik National Park require a Parks Canada pass, and backcountry campsites must be reserved in advance through the Parks Canada Reservation Service.