Two major rivers that start in Canada - the Yukon and the Columbia - cross the international border. Nine Canadian rivers flow farther than 1,000 km:

River	Length	Flows into
Athabasca	1,231 km	Arctic Ocean
Columbia	2,000 km, the first 800 of which are in Canada	Pacific Ocean (via USA)
Fraser	1,370 km	Pacific Ocean
Mackenzie	4,241 km	Arctic Ocean
Nelson	2,575 km, including the Churchill River	Hudson Bay - Atlantic Ocean
Ottawa	1,271 km	St. Lawrence River - Atlantic Ocean
St. Lawrence	3,058 km, including the Great Lakes - Superior, Michigan, Huron, Erie, Ontario	Atlantic Ocean
Saskatchewan	1,939 km	Hudson Bay - Atlantic Ocean
Yukon	3,185 km	Pacific Ocean (via USA)