[10] It was founded in 1631 by Siberian Cossack ataman Ivan Galkin, who built an ostrog (fort) there.

Mineral springs to the west of the town were reportedly discovered as early as the 17th century by Yerofey Khabarov and a spa was built at the site in 1925.

In the early 20th century Ust-Kut served as a destination for political exiles, most notably Leon Trotsky.

[citation needed] Ust-Kut remained the end of the line until 1974, when construction work started to extend the railway, now known as the Baikal–Amur Mainline, east toward Lake Baikal and beyond.

During the summer months, passenger ferries depart downriver from Ust-Kut to Yakutsk and Tiksi.