Mannus is a Germanic mythological figure attested by the 1st century AD Roman historian Tacitus in his work Germania. According to Tacitus, Mannus is the son of Tuisto and the progenitor of the three Germanic tribes Ingaevones, Herminones and Istvaeones.

Tacitus (Germania, chapter 2) explicitly mentions the names of these Germanic tribes, claiming descent from Mannus:

The name of this deity means human or man (as in Homo sapiens). It stems from the same root as the Indian Manu, progenitor of humanity, first holy king to rule this earth who saves mankind and the Vedas and the priesthood from the universal flood.

This deity shares his name with the 20th rune of the Elder Futhark. It appears in the 3rd ætt or family of the futhark, along with such other "god-runes" as Tiwaz and Ingwaz. This aett thus reflects the "ancient hymns" as sung by the Iron Age Germanic peoples, in which Mannus is mentioned.

In the Eddas, Mannus seems to most closely resemble Heimdall (World's Brightness). In the opening passage of the Voluspa, men are referred to as being Heimdall's kin, while in the poem Rigsthula he is shown uniting each of the hierarchal ranks in siblinghood. Furthermore, while Mannus is remembered as being the father of both Odin and Frey, Heimdall is remembered as being one of the Aesir, but also to have qualities directly linked to the Vanir and to exist in a close paternal relationship to Freyja.