Icelandic (íslenska) is a North Germanic language spoken in Iceland. It is an inflected language with four cases: nominative, accusative, dative and genitive. Its closest relative is Faroese and can be somewhat understood by some Norwegians as well, depending on their dialect and education.

While most Western European languages have reduced greatly the extent of inflection, particularly in noun declension, Icelandic retains an inflectional grammar comparable to that of Latin, Ancient Greek, or more closely, Old Norse and Old English.

Written Icelandic has changed relatively little since the 13th century. As a result of this, and of the similarity between the modern and ancient grammar, modern speakers can still understand, more or less, the original sagas and Eddas that were written some eight hundred years ago. This ability is sometimes mildly overstated by Icelanders themselves, most of whom actually read the Sagas with updated modern spelling and footnotes - though otherwise intact. This old form of the language is called Old Icelandic, but also commonly equated to Old Norse, an umbrella term also known as "Danish Tongue" used for the common Scandinavian language of the Viking era.

The Icelandic alphabet is notable for its retention of two old letters which no longer exist in the English alphabet: þ (thorn or thott) and ð (eth or edh), representing the voiceless and voiced "th" sounds as in English thin and this respectively. The complete Icelandic alphabet is:

A Á B D Ð E É F G H I Í J K L M N O Ó P R S T U Ú V X Y Ý Þ Æ Ö a á b d ð e é f g h i í j k l m n o ó p r s t u ú v x y ý þ æ ö   (32 letters)

The preservation of the Icelandic language is taken seriously by the Icelanders — rather than borrow foreign words for new concepts, new Icelandic words are diligently forged for public use.