In Greek mythology, Andromeda is the daughter of Cepheus, the king of Aethiopia, and his wife, Cassiopeia. When Cassiopeia boasts that she is more beautiful than the Nereids, Poseidon sends the sea monster Cetus to ravage the coast of Aethiopia as divine punishment. Queen Cassiopeia understands that chaining Andromeda to a rock as a human sacrifice is what will appease Poseidon. Perseus finds her as he is coming back from his quest to decapitate Medusa, and brings her back to Greece to marry her and let her reign as his queen. With the head of Medusa, Perseus petrifies Cetus to stop it from terrorizing the coast any longer.
Perseus defends Andromeda from the monster Cetus by pelting it with stones. Corinthian amphora, 575–550 BC
Andromeda being tied for sacrifice. Apulian red-figure vase, c. 430–420 BC
Perseus holds up Medusa's head so Andromeda may safely see its reflection in the pool below. Fresco, 1st century AD, Pompeii
Princess and dragon is an archetypical premise common to many legends, fairy tales, and chivalric romances. Northrop Frye identified it as a central form of the quest romance.
Ruggiero Rescuing Angelica, an illustration for Orlando Furioso by Gustave Doré
Russian civil war propaganda poster from 1919: White Russian knight is fighting the Red Russian dragon
Perseus Freeing Andromeda After Killing Cetus, 1st century AD fresco from the Casa Dei Dioscuri, Pompeii.