The Ounasjoki is the Kemijoki's largest tributary and is Finland's longest single river tributary. It is also the largest river entirely within its borders. Ounasjoki is approximately 299.6 km in length, and the catchment area is 13968 km2, 27% of the Kemijoki catchment area.

Course

The Ounasjoki originates at Ounasjärvi lake in Enontekiö. It flows first eastwards through Periläjärvi lake and turns south after some seven kilometres. The river then follows southern-southeasterly course until its confluence with the Kemijoki at Rovaniemi.

Tributaries

Left

Right

Fauna

Grayling, trout, pike and other fish typical to northern Finland are found in the Ounasjoki.