Zashiversk (; ) was a town north of the Arctic circle in what is now the Sakha Republic (formerly Yakutia), Russia. It was located on the right bank of the Indigirka River where the river makes a sharp bend around the town-site. It was founded in 1639. It served as a fortress town and then as an administrative center. In 1803 administrative functions were removed to Verkhoyansk. Subsequently the town suffered repeated epidemics of smallpox. It was completely depopulated by 1898 (one source says by 1863).