In Norse mythology, Ymir, Aurgelmir, Brimir, or Bláinn is a primeval being born of primordial elemental poison and the ancestor of all jötnar. Ymir is attested in the Poetic Edda, compiled in the 13th century from earlier tradition material, in the Prose Edda, written by Snorri Sturluson in the 13th century, and in the poetry of skalds. Taken together, several stanzas from four poems collected in the Poetic Edda refer to Ymir as a primeval being who was born from venom that dripped from the icy rivers Élivágar and lived in the grassless void of Ginnungagap. Ymir birthed a male and female from the pits of his arms, and his legs together begat a six-headed being. The gods Odin, Vili, and Vé fashioned the Earth (elsewhere personified as a goddess; Jörð) from his flesh, from his blood the ocean, from his bones the hills, from his hair the trees, from his brains the clouds, from his skull the heavens, and from his eyebrows the middle realm in which mankind lives, Midgard. In addition, one stanza relates that the dwarfs were given life by the gods from Ymir's flesh and blood (or the Earth and sea).
In the Prose Edda, a narrative is provided that draws from, adds to, and differs from the accounts in the Poetic Edda. According to the Prose Edda, after Ymir was formed from the elemental drops, so too was Auðumbla, a primeval cow, whose milk Ymir fed from. The Prose Edda states that three gods killed Ymir; the brothers Odin, Vili, and Vé, and details that, upon Ymir's death, his blood caused an immense flood. Scholars have debated as to what extent Snorri's account of Ymir is an attempt to synthesize a coherent narrative for the purpose of the Prose Edda and to what extent Snorri drew from traditional material outside of the corpus that he cites. By way of historical linguistics and comparative mythology, scholars have linked Ymir to Tuisto, the Proto-Germanic being attested by Tacitus in his 1st century AD work Germania and have identified Ymir as an echo of a primordial being reconstructed in Proto-Indo-European mythology.