The sagas (from Icelandic saga, plural sögur), are stories about ancient Scandinavian and Germanic history, about early Viking voyages, about migration to Iceland, and of feuds between Icelandic families. They were written in the Old Norse language, mainly in Iceland.

The texts are epic tales in prose, often with stanzas or whole poems in alliterative verse embedded in the text, of heroic deeds of days long gone, tales of worthy men, who were often Vikings, sometimes Pagan, sometimes Christian. The tales are usually realistic, except legendary sagas, sagas of saints, sagas of bishops and translated or recomposed romances. They are sometimes romanticised and fantastic, but always dealing with human beings one can understand.
The term saga originates from the Icelandic saga (pl. sögur), and refers to (1) "what is said, statement" or (2) "story, tale, history". It is cognate with the English word "say", and the German sagen. Icelandic sagas are based on oral traditions and much research has focused on what is real and what is fiction within each tale. The accuracy of the sagas is often hotly disputed. Most of the manuscripts in which the sagas are preserved were taken to Denmark and Sweden in the 17th century, but later returned to Iceland.

There are plenty of tales of kings (e.g. Heimskringla), every-day people (e.g. Bandamanna saga) and larger than life characters (e. g. Egils saga). The sagas describe a part of the history of some of the Nordic countries (e.g. the last chapter of Hervarar saga). The British Isles, northern France and North America are also mentioned. It was only recently (start of 20th century) that the tales of the voyages to America were authenticated.

Most sagas of Icelanders take place in the period 930–1030, which is actually called söguöld (Age of the Sagas) in Icelandic history. The sagas of kings, bishops, contemporary sagas and so on, of course have their own time frame. Most were written down between 1190 to 1320, sometimes existing as oral traditions long before, others are pure fiction, and for some we do know the sources: The author of King Sverrir's saga had met the king and used him as a source. The Mythology theory of saga origin maintains that the plots and characters were heavily influenced by mythological material associated with the local landscape.