In Norse mythology, Narfi is a son of Loki, referred to in a number of sources. According to the Gylfaginning section of Snorri Sturluson's Prose Edda, he was also called Nari and was killed by his brother Váli, who was transformed into a wolf; in a prose passage at the end of the Eddic poem "Lokasenna", Narfi became a wolf and his brother Nari was killed.
In chapter 50 of Gylfaginning, to punish Loki for his crimes, the Æsir turn his son Váli into a wolf and he dismembers his brother, "Nari or Narfi", whose entrails are then used to bind their father.
Nú var Loki tekinn griðalauss ok farit með hann í helli nökkvorn. Þá tóku þeir þrjár hellur ok settu á egg ok lustu rauf á hellunni hverri. Þá váru teknir synir Loka, Váli ok Nari eða Narfi. Brugðu æsir Vála í vargslíki ok reif hann í [sundr] Narfa, bróður sinn. Þá tóku æsir þarma hans ok bundu Loka með yfir þá þrjá [egg]steina, einn undir herðum, annarr undir lendum, þriði undir knésfótum, ok urðu þau bönd at járni. — Eysteinn Björnsson's edition
Now Loki was taken truceless, and was brought with them into a certain cave. Thereupon they took three flat stones, and set them on edge and drilled a hole in each stone. Then were taken Loki's sons, Váli and Nari or Narfi; the Æsir changed Váli into the form of a wolf, and he tore asunder Narfi his brother. And the Æsir took his entrails and bound Loki with them over the three stones: one stands under his shoulders, the second under his loins, the third under his houghs; and those bonds were turned to iron. — Arthur Gilchrist Brodeur's translation
The prose colophon to "Lokasenna" has a summary of the same story, probably derived from Snorri; In this version, there is no mention of a brother named Váli, Nari is the brother who is killed, Narfi transforms into a wolf, and the connection is not explained. The name Nari has often been changed to Váli to better conform to the Prose Edda account; for example in Guðni Jónsson's 1954 edition and in Henry Adams Bellows' 1923 English translation.