Gullinbursti (“Golden Bristles”) is Freyr’s boar in Norse mythology. The boar is faster than any horse, maybe with the exception of Odin’s horse Sleipnir. Its bristles are made from gold, so even in the middle of the night, the bristles in its mane will light up the sky as if it were day.
The boar was made by the two dwarves Brokkr and Eitri during a bet with the trickster Loki. He had claimed that they would never be able to make anything as good as the Sons of Ivaldi, who had made Skidbladnir, Odin’s spear, and Sif’s golden hair.
As Snorri Sturluson wrote in the Prose Edda (Skáldskaparmál):
Eitri laid a pigskin in the forge and told Brokkr to blow, and not stop before he took it out of the forge again. But when he left the workshop for a moment, a fly landed on Brokkr’s hand and bit him, but Brokkr ignored the fly and kept on working until Eitri came back, and took out the finished boar with its bristles of gold. The fly was Loki, who tried to sabotage the boar so he could win the bet.
According to the skaldic poem Húsdrápa by Úlfr Uggason, Freyr rode Gullinbursti to Baldur’s funeral. Snorri is of a different opinion and wrote in Gylfaginning, that Freyr rode to the funeral in a chariot pulled by the boar.