Lagarfljót (also called Lögurinn) is a lake situated in the east of Iceland near Egilsstaðir. Its surface measures 53 square kilometres (20 sq mi) and it is 25 kilometres (16 mi) long; its greatest width is 2.5 km (1.6 mi) and its greatest depth 112 m (367 ft). The River Lagarfljót flows through this lake.
The biggest forest in Iceland, Hallormsstaðaskógur is found near the lake as well as a waterfall, Hengifoss. Hengifoss, at 118 m (387 ft), is one of the tallest waterfalls in the country. Below it is another waterfall called Litlanesfoss.
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.