The fauna of Iceland numbers thousands of species. More than 2,000 freshwater and terrestrial animal species live in Iceland, and over 2,500 marine animal species have been found in Iceland’s exclusive economic zone. The total figure is certainly much higher, as many species-rich animal groups found in Iceland have been little studied.

During the Tertiary, the biota of Iceland was very different than today. Iceland’s biota was significantly more diverse before glaciation wiped out virtually all life here. Given Iceland’s geographical position and climate, many more small animals (particularly invertebrates) should be able to thrive in terrestrial and freshwater habitats. The diversity of Iceland’s biota pales in comparison to that of other countries in the North Atlantic region, where animal species number in the tens of thousands. The most probable reason is Iceland’s isolation, being a remote island far from the continents. Opportunities for insects and other small terrestrial and freshwater animal species to reach Iceland after the end of the Ice Age have been limited. The same is true of plants, and this places still greater constraints on the prospects of prospective invertebrate colonisers in Iceland, since many invertebrates rely on the presence of specific plants and vegetation types. The postglacial terrestrial and freshwater fauna of Iceland seems to have arrived almost exclusively from Europe, with a few exceptions from North America.

The Icelandic Institute of Natural History (IINH) is responsible for diverse research in the field of zoology. Emphasis is placed on basic research on Icelandic wildlife: information on the species found in Iceland, their geographical distribution, and their habitat. Research is also carried out on the life and ecology of important animal species, their communities, and interactions with plants and various environmental factors. This research includes regular monitoring of birds and wild mammals, in addition to taxonomic research on marine and land invertebrates. Summary data on the wildlife of Iceland, including information on species diversity and their distribution and habitat, are saved in the IINH databases. Pages on the IINH website on the different animal groups within the animal classification system are partially based on such data. The IINH Scientific Collections preserve several million specimens, from all animal groups found in nature in Iceland. The IINH also compiles Red Lists for the biota of Iceland, based on the guidelines of the International Union for Conservation of Nature (IUCN).