Lancaster Sound, an arm of Baffin Bay and a major passage through the Arctic Archipelago, is 400 km long and some 100 km wide. It lies at the north end of Baffin Island and is connected to Barrow Strait on the west. As a result of the interaction of currents, the sound is rich in nutrients and supports a biologically varied community of birds, mammals and fish. At Bylot Island, which lies at its eastern end, it provides breeding grounds for some 3 million seabirds alone. The area has provided sustenance for Inuit cultures for thousands of years: ringed seals, walrus and polar bears, and narwhals, belugas, killer and bowhead whales. Arctic fox is trapped in almost every inlet, and arctic char is taken at the mouths of rivers.

European interest began in the 17th century, with the search for the Northwest Passage, and William Baffin was likely the first to record the existence of the sound (1616). It was named for English navigator Sir James Lancaster (d 1618). Whaling became important at the beginning of the 19th century. Later that century trading posts were established at Button Port, Albert Harbour, Arctic Bay, Pond Inlet and Dundas Harbour. In the late 20th century lead-zinc ore was mined at Nanisivik. With icebreakers, the passage is open to local shipping from mid summer to early fall.

Increased human activity threatens the area's wildlife, which is concentrated at a few sites and therefore highly vulnerable. However, Sirmilik National Park protects part of the Lancaster Sound marine region.