|Statue of Perseus|
holding the severed head
Perseus is a demi-god of Ancient Greece. (Literally, half -god: His father was Zeus, and his mother was a mortal woman, Danae.)
Perseus slays Medusa. Medusa was a Gorgon, technically not a dragon. But dragons are sometimes depicted as creatures with multiple serpent heads spring from their neck. Medusa with her serpent hair may be based on dragon legends.
When Perseus is returning home he comes upon Andromeda, a young princess chained to a rock about to be attacked by a sea serpent, Cetus. She is being sacrificed because the Delphi oracle has said it was the only way to rid the kingdom of a rampaging dragon. Perseus kills this sea dragon. The rescued maiden becomes Perseus' bride
See a detailed discussion about why I consider these two beasts to be dragons at The Dragon Files: Do Humans Have Dragon DNA?
You can also read a detailed account of the Life of Perseus at Who is Perseus? Ancient Greek Dragon Slayer
A movie, The Clash of the Titans tells the story of Perseus.