The Tuostakh (Russian: Туостах; Yakut: Туостаах, Tuostaax) is a river in the Verkhoyansk District, Sakha (Yakutia), Russia.

It heads roughly northwest meandering slowly across a very swampy area dotted with small lakes where it divides into channels.

After turning west in a wide arch at the feet of the southern side of the Kisilyakh Range the river joins the right bank of the Adycha downstream from the Charky.

The river freezes in October and stays under thick ice until the end of May or early June.

There are about 40 ice fields in the Tuostakh basin, with a total surface area of 40 km2 (15 sq mi).