In Germanic heroic legend and folklore, Fáfnir is a worm or dragon slain by a member of the Völsung family, typically Sigurð. In Nordic mythology, he is the son of Hreiðmarr, and brother of Regin and Ótr and is attested throughout the Völsung Cycle, where, Fáfnir slays his father out of greed, taking the ring and hoard of the dwarf Andvari and becoming a worm or dragon. Fáfnir's brother Regin later assisted Sigurð in obtaining the sword Gram, by which Fáfnir is killed. He has been identified with an unnamed dragon killed by a Völsung in other Germanic works including Beowulf, the Nibelunglied and a number of skaldic poems. Fáfnir and his killing by Sigurð are further represented in numerous medieval carvings from the British Isles and Scandinavia, and a single axe head in a Scandinavian style found in Russia. The story of Fáfnir has continued to have influence in the modern period, such as in the works of J.R.R Tolkien, who drew inspiration from the tale of Fáfnir in his portrayals of Smaug and Gollum.

Germanic heroic legend is the heroic literary tradition of the Germanic-speaking peoples, most of which originates or is set in the Migration Period. Stories from this time period, to which others were added later, were transmitted orally, traveled widely among the Germanic speaking peoples, and were known in many variants. These legends typically reworked historical events or personages in the manner of oral poetry, forming a heroic age. Heroes in these legends often display a heroic ethos emphasizing honor, glory, and loyalty above other concerns. Like Germanic mythology, heroic legend is a genre of Germanic folklore.