The sonargǫltr or sónargǫltr was the boar sacrificed as part of the celebration of Yule in Germanic paganism, on whose bristles solemn vows were made in some forms of a tradition known as heitstrenging.

Hervarar saga ok Heiðreks refers to the tradition of swearing oaths on Yule Eve by laying hands on the bristles of the boar, who was then sacrificed in the sonar-blót:

Ok skyldi þeim gelti blóta at sónarblóti. Jólaaptan skyldi leiða sónargöltinn í höll fyrir konúng; lögðu menn þá hendr yfir burst hans ok strengja heit.

And they would sacrifice a boar in the sonarblót. On Yule Eve the sonar-boar was led into the hall before the king; then people laid their hands on its bristles and made vows.

One of the prose segments in "Helgakviða Hjörvarðssonar" adds that the oaths were sworn while drinking the bragarfull toast:

Um kveldit [jólaaftan] óru heitstrengingar. Var fram leiddr sónargöltr. Lögðu menn þar á hendr sínar ok strengðu menn þá heit at bragarfulli.

That evening [of Yule Eve] the great vows were taken; the sacred boar was brought in, the men laid their hands thereon, and took their vows at the king's toast.

In Ynglinga saga the sonarblót is used for divination (til frettar).