In Norse mythology Mani ("Moon" in Old Norse) was the personification of the Moon. This is mentioned in the poetic Edda and the prosaic Edda, compilations written in the 12th century by Snorri Sturluson from older oral traditions.
In stanza 23 of the poem Vafþrúðnismál, the god Odin (in the form of Gagnráðr) challenges the jotun Vafþrúðnir with a question about the origins of the Sun and Moon, which he describes as traveling over men. Vafþrúðnir replies that Mundilfari is the father of Sól and Máni, and that they must travel the heavens every day so that men can count the years:
Mundilfæri is called, he who is father of the Moon,
and of the eternal Sun; through the heavens every day they travel,
to count the years for men.
In stanza 39 of the poem Grímnismál, Odin (in the form of Grimnir) relates that both the Sun and the Moon are pursued across the sky by wolves; Sun, called as the "bright god" is pursued by Sköll to the "protecting forests," while Moon is pursued by Hati Hróðvitnisson.
In stanza 13 of the poem Alvíssmál, the god Thor interrogates the dwarf Alvíss about the Moon, asking him what she is called in each of the worlds. Alvíss answers that it is called "moon" by men, "flame" by the gods, "the wheel" in Hel, "the hasty one" by the jotun, "the bright one" by the dwarves and "the year-counter" by the elves.
In Gylfaginning, prosaic Edda, Máni is mentioned in three chapters. In chapter 8, the fifth stanza of Völuspá is quoted, where the Sun and the Moon are mentioned during the creation of the world.
In chapter 11, it is mentioned that Máni and her sister are the children of a man named Mundilfari. The children were so beautiful that Mundilfari called them "Moon" and "Sun", which was seen by the gods as an act of arrogance that annoyed the gods so much that they placed them in the heavens. There Máni "guides the path of the moon and controls its waxing and waning."
It is further mentioned that Máni is followed through the heavens by the brothers, Hjúki and Bil "as may be seen from earth," whom he took from the earth while they were gathering water at a well. In Chapter 51, the events of Ragnarök are recounted, including Máni and his sister being devoured by the wolves that pursue them.
In Skáldskaparmál, Prosaic Edda, Sól is mentioned in chapter 26 as "Máni's sister", and in chapter 56 the Moon is given names: "lunula", "crescent", "waning", "year-counter", "clipped", "bright", "twilight", "rushing", "squinter", and "glittering".