The Siberian river system ranked fifth by length and flowing to the Kara Sea is the Yenisei.
The Yenisei rises through a network of headwaters in Mongolia and southern Siberia, then runs north across Russia. Its main named course begins at Kyzyl, where the Great Yenisey and Little Yenisey meet, and continues to the Yenisey Gulf, which opens into the Kara Sea. When its distant headwaters are counted, the full system stretches for roughly 5,000 km.
The river is the largest of the three great Siberian rivers draining into the Arctic Ocean. The other two are the Ob to the west and the Lena to the east. Its basin includes much of central Siberia and separates the Western Siberian Plain from the Central Siberian Plateau.
“Yenisei” and “Yenisey” are both accepted English transliterations. The river is also sometimes confused with the Ob because both empty into the Kara Sea, but the fifth-place ranking identifies the Yenisei.