The Sellyakh ( or ; , ) is a river in the Sakha Republic (Yakutia), Russia. It is long âÂÂincluding the Ilin-Sellyakh () at its headâ and its drainage basin covers .
The river flows north of the Arctic Circle, across territories of the Ust-Yansky District with areas of permafrost. The lower course of the river belongs to the Yana Delta Ramsar wetland site. There are no settlements along its course. The nearest town is Tumat.
The Sellyakh has its sources in the western part of the Yana-Indigirka Lowland, East Siberian Lowland. The river is formed at the confluence of long Ilin-Sellyakh and long Arga-Sellyakh, also known as Sygynakhtaakh (áÃÂóÃÂýðàÃÂððà). The Sellyakh flows roughly northwestwards across very swampy flatland dotted with small lakes, to the northeast of the Nuchcha. Its channel meanders strongly and in its lower course the river turns north, its floodplain roughly parallel to the Chondon that flows northwards to the west. Finally the river ends in the Sellyakh Bay of the Laptev Sea. It shares a common mouth system with the Bilir, to the southwest of the mouth of the Danilkina.
The main tributaries of the Sellyakh are the long Tut-Balyktakh (âÃÂÃÂÃÂ-ÃÂðûÃÂúÃÂððà) and the long Syuyuryukteekh (áÃÂÃÂÃÂÃÂúÃÂÃÂÃÂà) on the right, as well as the long Sygynastakh (áÃÂóÃÂýðÃÂÃÂððà) on the left. There are over 6,000 lakes in the Sellyakh basin. The river is frozen between early October and early June.