The Mackenzie River is the largest river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 system in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. It flows through a vast, isolated region of forest and tundra

Tundra

In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...

 entirely within the country's Northwest Territories

Northwest Territories

The Northwest Territories is a federal territory of Canada.Located in northern Canada, the territory borders Canada's two other territories, Yukon to the west and Nunavut to the east, and three provinces: British Columbia to the southwest, and Alberta and Saskatchewan to the south...

, although its many tributaries reach into four other Canadian provinces and territories. The river's mainstem

Mainstem

Mainstem may refer to:* Mainstem is the principal watercourse in a riverine drainage system with multiple named streams.* Mainstem bronchus is a medical term for a part of the respiratory system....

 runs 1738 kilometres (1,079.9 mi) in a northerly direction to the Arctic Ocean

Arctic Ocean

The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...

, draining a vast area nearly the size of Indonesia

Indonesia

Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

. It is the largest river flowing into the Arctic from North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, and with its tributaries is one of the longest rivers in the world.
Rising out of the marshy western end of Great Slave Lake

Great Slave Lake

Great Slave Lake is the second-largest lake in the Northwest Territories of Canada , the deepest lake in North America at , and the ninth-largest lake in the world. It is long and wide. It covers an area of in the southern part of the territory. Its given volume ranges from to and up to ...

, the Mackenzie River flows generally west-northwest for about 300 km (186.4 mi), passing the hamlets of Fort Providence

Fort Providence, Northwest Territories

Fort Providence is a hamlet in the South Slave Region of the Northwest Territories, Canada...

 and Brownings Landing.