Thor

Thor was a deity in Norse mythology. His father was Odin.

The Third Doctor and Jo Grant met Thor in 141. He was actually a human son of Odin, High King of all Sweden, who was believed to be a god due to the power of Gungnir or Spear of Destiny, an alien artefact he possessed.

The Master, under the alias of Frey, influenced the Vanir, a tribe of Vikings in 141 to fight Odin and Thor and the Third Doctor so that he could get Gungnir. The Doctor explained to Jo at the time that Norse mythology probably came from real adventures of early Viking history, as here the fight between Vanir and Odin's folk. (PROSE: The Spear of Destiny)

Thor attended Bonjaxx's birthday party at Maruthea. (COMIC: The Incomplete Death's Head)

Behind the scenes
While Thor originated in Norse Mythology, he is also a superhero in Marvel comics. Thor, as indicated by his winged helmet and Mjolnir, appears with other Marvel heroes in part 11 of The Incomplete Death's Head. Contrary to the standard Marvel comics interpretation, this Thor has a beard.