18,050 m3/s (637,000 cu ft/s)[5] (Period of data: 1940–2017) 588 km3/a (18,600 m3/s)[7] The Yenisey or Yenisei[8] (/ˌjɛnɪˈseɪ/ YEN-iss-AY; Russian: Енисе́й, pronounced [jɪnʲɪˈsʲej])[a] is the fifth-longest river system in the world, and the largest to drain into the Arctic Ocean.

Rising in Mungaragiyn-gol in Mongolia, it follows a northerly course through Lake Baikal and the Krasnoyarsk Dam before draining into the Yenisey Gulf in the Kara Sea.

They provide a wetland habitat for rare and endangered birds and are an internationally important nesting and breeding area for several types of waterfowl.

[16] Most fish found in the Yenisey basin are relatively widespread Euro-Siberian or Siberian species, such as northern pike (Esox lucius), common roach (Rutilus rutilus), common dace (Leuciscus leuciscus), Siberian sculpin (Cottus poecilopus), European perch (Perca fluviatilis) and Prussian carp (Carassius gibelio).

The basin is also home to many salmonids (trout, whitefish, charr, graylings, taimen and relatives) and the Siberian sturgeon (Acipenser baerii).

Both the Ob and Yenisey mouths feed into very long inlets, several hundred kilometres in length, which are shallow, ice bound and prone to high winds and thus treacherous for navigation.

The first recreation team to navigate the Yenisey's entire length, including its violent upper tributary in Mongolia, was an Australian-Canadian expedition completed in September 2001.

The Ket, numbering about 1000, are the only survivors today of those who originally lived throughout central southern Siberia near the river banks.

The modern Ket lived in the eastern middle areas of the river before being assimilated politically into Russia during the 17th through 19th centuries.

[28] In 1862 Paul Theodor von Krusenstern attempted to navigate with two ships from Murmansk through the Kara Sea to the delta of the river Yenissei, but unfortunately was shipwrecked before obtaining success.

It is believed that the name of the Yenisei River was transmitted, either directly or indirectly, from Samoyed-speaking peoples in the region with whom the Russians had contact.

[46] Additionally, by the end of the 16th century, the Yenisei River was already known to Dutch navigators, who referred to it as "Gilissi", "Gelissi", or "Geniscea", among other names.

[48] Unlike in Dutch, the Russian spelling has been relatively stable since the 17th century, with only minor variations such as "Yeniseya" (Енисея) or "Yenisya" (Енися).

Renowned linguist Max Vasmer, for instance, has suggested that the Nganasan word "Jentajea", the Enets "Jeddosi", and the Selkup "N'andesi", all meaning "Yenisei River", might correspond to unidentified Samoyed languages,[50] probably quoted Matthias Castrén's vocabulary.

[51] V. K. Nikonov has proposed that the word could derive from "iondessi" (иондесси), meaning "big river" in Selkup, Khanty, or even Evenki.

[54] Researchers are encouraged to conduct more detailed studies based on proper contemporary linguistic sources and historical documents.

[55] Studies have shown that the Yenisey suffers from contamination caused by radioactive discharges from a factory that produced bomb-grade plutonium in the secret city of Krasnoyarsk-26, now known as Zheleznogorsk.