Hofsjökull is the third largest ice cap in Iceland after Vatnajökull and Langjökull and the largest active volcano in the country. It is situated in the west of the Highlands of Iceland and north of the mountain range Kerlingarfjöll, between the two largest glaciers of Iceland. It covers an area of 925 km², reaching 1,765 m (5,791 ft) at its summit. The subglacial volcano is a shield type with caldera.

Hofsjökull is the source of several rivers including the Þjórsá, Iceland's longest river.

In the southeast of Iceland, between the easternmost glacier tongue of Vatnajökull and Þrándarjökull, there is a smaller glacier (area about 4 km2), which is also called Hofsjökull.

In 2015, Hofsjökull increased in mass, the first time in 20 years this had happened.