The Olguydakh (Russian: Олгуйдах; Yakut: Олгуйдаах), is a river in Yakutia (Sakha Republic), Russia.

It is a left hand tributary of the Akhtaranda, part of the Vilyuy basin.

[2][3] An area where mysterious events reportedly took place lies near the abandoned Olguydakh village on the banks of the lower course of the river.

It originates in the northeastern end of lake Toymoku (Yakut: Тоймоку) of the Vilyuy Plateau.

[6] The main tributary of the Olguydakh is the 80 kilometres (50 mi) long Aallaakh (Ааллаах) from the left.