Heimdallr (Old Norse: Heimdallr) is the watchman of the gods, stationed at the boundary of Ásgarðr where he guards the Bifröst bridge. He is described in Gylfaginning as requiring less sleep than a bird, possessing sight and hearing of extraordinary acuity — able to see and hear grass growing in fields and wool growing on sheep. He owns the horn Gjallarhorn, whose blast will summon the gods to Ragnarök; Völuspá states it is kept under the world-tree Yggdrasil. His hall Himinbjörg (Sky-Cliffs) sits at the point where the Bifröst meets the sky, as named in Grímnismál.

Heimdallr’s most developed mythological narrative is the Eddic poem Rígsþula, in which he travels through Miðgarðr under the name Rígr, fathering the three classes of mankind — thralls, peasants, and nobles — through successive unions with human women. The poem is preserved in the Codex Wormianus with a prose header attributing the name Rígr to Heimdallr.

The Prose Edda preserves the tradition that Heimdallr has nine mothers, all sisters — elaborated in Hyndluljóð. A kenning in skaldic verse describes him as hvítastr ása (whitest of the Æsir). At Ragnarök, Heimdallr and Loki are destined to kill each other — a detail consistent across Völuspá and Gylfaginning.