What is the name of the golden boar that belongs to Freyr?

The golden boar belonging to Freyr is Gullinbursti.

Gullinbursti’s Old Norse name is commonly interpreted as “Gold Mane” or “Golden Bristles.” Its shining bristles glowed in darkness, making the boar a fitting companion for Freyr, a god associated with prosperity, fertility, sunshine, and good harvests.

The boar was forged by the dwarfs Eitri and Brokkr during a contest prompted by Loki. Eitri placed a pigskin in a furnace while Brokkr worked the bellows. The resulting boar could travel swiftly over land and water, and Freyr used it to draw a chariot. Another name for the animal is Slíðrugtanni, meaning something like “Sharp Tooth” or “Fearsome Tooth.”

Gullinbursti is sometimes confused with Hildisvíni, the boar associated with Freyja, or Sæhrímnir, the ever-renewed boar eaten by the einherjar in Valhalla. Those are different mythological animals. The story of Gullinbursti’s creation appears in the Skáldskaparmál section of Snorri’s Prose Edda.