In the Poetic Edda poem Hávamál, Odin hangs on the world tree for nine nights. The poem describes Odin sacrificing himself to himself while suspended on the tree, wounded by a spear and deprived of food and drink.
This ordeal leads to his discovery of the runes. In the relevant passage, Odin says that he looked down and took up the runes, gaining knowledge through suffering and isolation. The world tree is not named directly in every translation, but it is conventionally identified as Yggdrasil.
The number nine is strongly associated with Odin and Norse cosmology. It appears in other literary and mythological contexts, including the nine worlds often linked with Yggdrasil and Heimdall’s nine mothers. Translators may vary in wording, but the duration is consistently nine nights.
Hávamál means “The Words of the High One,” with “the High One” being Odin. It is preserved in the medieval Icelandic manuscript Codex Regius and combines wisdom sayings, social advice, and mythic autobiography.