Mani is the Norse personification of the moon, who guides it on its nightly course, and his sister Sol drives the sun, an arrangement that inverts the more familiar Mediterranean gendering, for in Norse and wider Germanic tradition the moon is masculine and the sun feminine, a pattern still preserved in the grammatical gender of the German words der Mond and die Sonne. The Norse cosmos sets both luminaries in flight: each is pursued by a wolf, and at Ragnarok the wolf Hati is fated to catch and swallow Mani.
The poem Vafthrudnismal names him among the ordered features of the sky, and Snorri adds a folktale-like detail in which Mani takes up two children, Bil and Hjuki, who are seen following him across the heavens, an image sometimes connected with later European lore of figures in the moon. Snorri's episode of Bil and Hjuki, the two children Mani takes up from earth to follow him across the sky, has long invited comparison with the English nursery rhyme of Jack and Jill tumbling down a hill with a pail of water, a connection first proposed by nineteenth-century folklorists and still debated rather than confirmed, since the rhyme's own written record does not appear until the eighteenth century, many centuries after Snorri wrote. The Norse pairing of a masculine moon and feminine sun, opposite the pattern found in Greek, Roman and many other Indo-European traditions, is also preserved outside mythological poetry in the ordinary grammatical gender of Old Norse and modern Icelandic nouns for sun and moon, evidence that the association ran through everyday language and not only poetic invention.