Lagarfljót (Icelandic pronunciation: [ˈlaːɣarˌfljouːt] ⓘ) also called Fljótið [ˈfljouːtɪθ] is a river situated in the east of Iceland near Egilsstaðir.

The 27 MW Lagarfossvirkjun hydropower station is located at its lower end.

[1] The biggest forest in Iceland, Hallormsstaðaskógur is found near the river as well as a waterfall, Hengifoss.

Hengifoss, at 128 m (420 ft), is one of the tallest waterfalls in the country.

As with the Scottish lake Loch Ness, a cryptid serpent, called Lagarfljótsormurinn by locals, is believed by some to live in the depths of Lagarfljót.