giant
Bestla
A giantess, daughter of Bölþorn, wife of Borr and mother of Odin, Vili and Vé. Through her the chief god is half giant by birth.
Bestla is Odin's mother. Snorri's Gylfaginning says that Borr "wedded the woman named Bestla, daughter of Bölthorn the giant", and that their sons were Odin, Vili and Vé Gylfaginning 6. The ruler of the gods is therefore the son of a giantess, and the line of the Æsir mixes with the giants from its first generation.
The only other mention in the Eddas is in Hávamál. Describing what he gained from hanging on the tree, Odin says he learned nine mighty songs "from the son of Bolthorn, Bestla's father" Hávamál 141. The unnamed son is Bestla's brother, Odin's maternal uncle. A skaldic verse quoted in Skáldskaparmál calls Odin "Bestla's Offspring" Skáldskaparmál 2, so the relationship was a known poetic resource.
That is all. No source describes Bestla herself, tells how she met Borr, or says what became of her. Some scholars have suggested that the uncle in Hávamál is Mímir, which would make Odin's adviser his mother's brother, a close tie in early Germanic society. The texts never say so.
In the sources
Quoted from the hosted translations; each line is checked against the text when the site is built. Select a reference to read it in context.
He begat a son called Borr, who wedded the woman named Bestla, daughter of Bölthorn the giant; and they had three sons: one was Odin, the second Vili, the third Vé.
Nine mighty songs I got from the son Of Bolthorn, Bestla's father