In Greek mythology Peleus was the king of the Myrmidons in Phthia, husband of the sea-nymph Thetis and father by her of Achilles. As a wedding present, Poseidon gave Peleus two immortal horses: Balius and Xanthus. Their wedding, however, was also the beginning of the quarrel that led to the judgement of Paris.
According to legend, Thetis had tried to make Achilles invincible by dipping him in the river Styx, but forgot to wet the heel she held him by, leaving him vulnerable so he could be killed by a blow to that heel. Homer, however, deliberately makes no mention of this; Achilles can not be a hero if he is not at risk. In an earlier and less popular version of the story, Thetis anointed the boy in ambrosia and put him on top of a fire to burn away the mortal parts of his body. She was interrupted by Peleus and abandoned both father and son in a rage. Peleus gave him to Chiron to raise.
Peleus was one of the Argonauts.