The mythology of North Germanic peoples was highly influential to J.R.R. Tolkien in the creation of his legendarium.
Races[]
The Elves and Dwarves, among other creatures featured less heavily in Tolkien's works, were originally (by name) mythological creatures of old Norse sagas.
Names[]
The Völsunga Saga is an ancient Norse writing which significantly influenced Tolkien's legendarium. The names of the Norse Dwarves, or dvergar, are listed in the Völuspá, and Tolkien used these names in The Hobbit: Dwalin, Bombur, Fili, Kili and so on. Gandalf (literally translated as "magic-elf") is also the name of one of the dvergar, though Gandalf himself is modeled after the god Odin.
The name Durin is from the name of Durinn, a dwarf of Norse mythology.
Events[]
The final battle prophesied at the end of the legendarium, Dagor Dagorath (the Final Battle), bears many resemblances to Ragnarök (literally "fate of the Gods"), the battle which destroys the Norse universe. Both battles result in a near-complete destruction of the world, from which a new world is created, inhabited by those who originally lived.
Places[]
Tolkien's legendarium centers on the history of Middle-earth, which draws its name from the Old Norse miðgarðr.
In the story of Wayland the Smith found in the Völundarkviða, three swan-maidens fly south over a Mirkwood to the place where they meet Wayland (or Welund) and his brothers.