The myth of Andromeda was treated in the homonymous tragedy of Euripides, of which many fragments have come down to us.
She was the daughter of Cepheus King of Ethiopia, and Cassiopeia, and was to be sacrificed as an expiatory victim for the sin of vanity committed by her mother against the goddesses. She was therefore bound to a rock, destined to die but was saved by Perseus. Just back from his expedition against Medusa, he fell in love with her and promised Cepheus that he would kill the monster the Gods had sent to scourge Ethiopia as punishment for Cassiopeia's sin, if he agreed to their marrying. Medusa was one of the three Gorgons, children of sea gods. These monsters had heads surrounded by snakes, tusks like wild boars, bronze hands and golden wings that allowed them to fly, but above all had the power to petrify whoever met their gaze. Also Phineus, who was Cepheus' brother, pretended to the young woman's hand, and therefore plotted against Perseus. The latter then turned the head of Medusa against his enemies, who were transformed into stone, and brought Andromeda as his wife to Argos.
According to a different version of the myth, reported by mythographer Conon, Cepheus ruled the land that later would be called Phoenicia after the name of Phoenix. Phoenix fell in love with Andromeda, who was also courted by her paternal uncle. Cepheus, not to displease his brother, at the same time preferring Phoenix as a husband for his daughter, devised a ruse: Andromeda, who was on the island where the goddess Aphrodite was worshipped, would be kidnapped by Phoenix on the ship called Whale. Andromeda however, ignoring the act devised by the two men, got frightened and began to throw loud cries for help. Perseus who was nearby, heard her cries and fell in love with her at first sight. Therefore he destroyed the ship, saved the girl and brought her to Tiryns, over which they reigned together.
The constellation was introduced by Ptolemy in the northern sky to the south of Cassiopeia and Pegasus, the Winged Horse. Its brightest stars form a straight line that extends diagonally of the "Square of Pegasus". Close to the "GAndromedae" star there is the famous Andromeda nebula, a galaxy very similar to the Milky Way, the only external galaxy visible with the naked eye and the nearest after the Magellanic Clouds, which are in actual fact considered as satellite galaxies of our solar system.