In Norse mythology, the einherjar (Old Norse "single (or once) fighters") are those who have died in battle and are brought to Valhalla by valkyries. In Valhalla, the einherjar eat their fill of the nightly-resurrecting beast Sæhrímnir, and are brought their fill of mead (from the udder of the goat Heiðrún) by valkyries. The einherjar prepare daily for the events of Ragnarök, when they will advance for an immense battle at the field of Vígríðr; the battle which the "ein" (here meaning single-time) refers to. Heimdall occasionally returned the best of Einherjar to Midgard or Jotunheim with the purpose of killing giants, but they were forbidden to talk with the living.

The einherjar are attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, the Prose Edda, written in the 13th century by Snorri Sturluson, the poem Hákonarmál (by the 10th century skald Eyvindr skáldaspillir) as collected in Heimskringla, and a stanza of an anonymous 10th century poem commemorating the death of Eric Bloodaxe known as Eiríksmál as compiled in Fagrskinna.