Final answer:
The Slave River flows from Lake Athabasca in northern Alberta, through the Northwest Territories, and empties into Great Slave Lake.
Step-by-step explanation:
The river that flows from Lake Athabasca in northern Alberta before emptying into Great Slave Lake is the Slave River.
Starting its journey in Lake Athabasca, the Slave River travels northwards across the province of Alberta and into the Northwest Territories, where it forms part of the boundary between them, before eventually draining into Great Slave Lake.
This river is an essential link in the vast network of waterways that traverse Northern Canada, connecting the Arctic and subarctic regions.