The Saskatchewan River (Cree: kisiskāciwani-sīpiy, "swift flowing river") is a major river in Canada, about 550 kilometres (340 mi) long, flowing roughly eastward across Saskatchewan and Manitoba to empty into Lake Winnipeg. Through its tributaries the North Saskatchewan and South Saskatchewan, its watershed encompasses much of the prairie regions of central Canada, stretching westward to the Rocky Mountains in Alberta and northwestern Montana in the United States. It reaches 1,939 kilometres (1,205 mi) to its farthest headwaters on the Bow River, a tributary of the South Saskatchewan in Alberta.