Which river is the longest to flow into the Arctic Ocean?

The Yenisei River is the longest river system flowing into the Arctic Ocean.

The Yenisei runs north through central Siberia before reaching the Yenisey Gulf, which opens into the Kara Sea and the Arctic Ocean. Its wider river system includes the Angara, Selenga and Ider rivers, giving it a total length of about 5,539 kilometres under the commonly used measurement.

The river rises in the Mongolian highlands and passes through Tuva and Russia. It separates the Western Siberian Plain from the Central Siberian Plateau and drains one of the world’s largest river basins. The Yenisei is also the central member of Siberia’s three great Arctic rivers, alongside the Ob and Lena.

A common mix-up is to choose the Ob or Lena, both of which also reach the Arctic Ocean. The Yenisei is generally accepted as the longest of the three when their complete river systems are measured.