Icelandic ( íslenska (help·info)) is a North Germanic language, the main language of Iceland. Its closest relative is Faroese.

Icelandic is an Indo-European language belonging to the North Germanic or Nordic branch of the Germanic languages. Historically, it was the westernmost of the Indo-European languages prior to the colonisation of the Americas. Icelandic, Faroese, Norn, and Norwegian formerly comprised West Nordic; Danish and Swedish comprised East Nordic. The Nordic languages are now divided into Insular Nordic and mainland Scandinavian languages. Norwegian is now grouped with Danish and Swedish because of its mutual intelligibility with those languages due to its heavy influence from them over the last millennium, particularly from Danish.

Most Western European languages have greatly reduced levels of inflection, particularly noun declension. In contrast, Icelandic retains a four-case synthetic grammar comparable to German. It is inappropriate to compare the grammar of Icelandic to that of the more conservative Baltic, Slavic, and Indic languages of the Indo-European family, many of which retain six or more cases, except to note that Icelandic is plagued by a wide assortment of irregular declensions. Icelandic also possesses many instances of oblique cases without any governing word, as does Latin. For example, many of the various Latin ablatives have a corresponding Icelandic dative. However, despite its arguable baggage, the remarkable conservatism of the Icelandic language and its resultant near-isomorphism to Old Norse (which is equivalently termed Old Icelandic by linguists) means that, to their delight, modern Icelanders can easily read the Eddas, sagas, and other classic Old Norse literary works created in the tenth through thirteenth centuries.