Guthorm or Guthormus was one of the earliest legendary Danish kings according to Saxo Grammaticus. He was a son of the Danish king, Gram, and a Swedish princess, Groa.
His father was slain by the Norwegian king, Svipdagr. After the incident, Svipdagr installed him as the puppet king of the Danes. However, his half-brother, Hading refused the offer and entered exile, later he returned and retook his father's kingdom, but lack of mentions of Guthorm implies that his half-brother died before his return. (It is also stated that when Hading defeated Svipdag, he had vengeance not only for his father but also his brother, supporting the idea that Guthorm had already died.)