The glaciers and ice caps of Iceland covered 11% of the land area of the country, up to about 2008. As of 2019^[update] this was down to 10%. They have a considerable impact on its landscape and meteorology. Glaciers are also contributing to the Icelandic economy, with a tourist market that includes glacier trips on snowmobiles and glacier hiking tours. However, the recent loss of ice due to climate change is an increasing concern in Icelandic society.

Glaciers can both grow in size and regress depending upon several factors of which climate and precipitation in the glaciers catchment are the most important. About 7,000 years ago, the Pleistocene ice from the last Ice Age over Iceland disappeared almost entirely, so the current glaciers in Iceland are not that old. In the case of Iceland as several large glaciers are over active volcanoes, geothermal melting can be a substantial component of the glacier ice mass balance. Accordingly Iceland's glacier area varies from year to year and some glaciers may grow while others regress. The tables below have to be interpreted considering such variations in time and do not include much other data that those who study glaciers would regard as important. Data that was gathered over many years in the 1890s, or even by the first complete aerial photographic survey between 1945 and 1946 is difficult to compare to the richer satellite studies and the on the ground measurements possible since the 1990's but such comparisons have been attempted. Even so there are gaps in the data (see Table 2). Two different definitions of a glacier are usually used in current research and much Iceland work is closer to the definition:

A perennial mass of ice, and possibly firn and snow, originating on the land surface by the recrystallization of snow or other forms of solid precipitation and showing evidence of past or present flow

— International Association of Hydrological Sciences,

An ice cap is a mass of glacial ice that covers less than 50,000 km² (19,000 sq mi) of land area covering a highland area and they feed outlet glaciers. Many Icelandic ice caps and glaciers lie above volcanoes, such as Grímsvötn and Bárðarbunga, which lie under the largest ice cap, Vatnajökull. The caldera of Grímsvötn is about 100 km² (39 sq mi) in area, and Bárðarbunga is about 60 km² (23 sq mi) meaning a large amount of ice, given mean icecap thickness of about 200 m (660 ft) is at risk of geothermal melting.

When volcanic activity occurs under the glacier, the resulting meltwater can lead to a sudden glacial lake outburst flood, known in Icelandic as a jökulhlaup. However jökulhlaups are more commonly caused by accumulation of meltwater due to geothermal activity underneath the glacier. Jökulhlaups occasionally trigger volcanic eruptions through the sudden release of pressure. These eruptions occur towards the end of the Jökulhlaup.

The glaciers are relevant enough in Icelandic geography that the four largest are represented blank in most of the maps of the administrative divisions of Iceland smaller than the regions.

Iceland is losing ice due to climate change. In 2008 its glaciers still covered 11% of the land area of the country, at about 11,100 km² (4,300 sq mi) out of the total area of 103,125 km² (39,817 sq mi). As of 2019^[update] this was down to 10%.