Who rescued Andromeda from a sea monster?

Perseus is the hero who rescued Andromeda from a sea monster. According to Greek mythology, Andromeda was chained to a rock as a sacrifice to the sea monster Cetus, sent by Poseidon as punishment to her mother Cassiopeia for boasting about Andromeda’s beauty. Perseus, returning from slaying the Gorgon Medusa, came upon Andromeda and, upon seeing her beauty, decided to save her. He defeated the monster using the head of Medusa, which turned Cetus to stone.

His heroic act not only saved Andromeda but also led to their marriage, showcasing themes of bravery and romantic heroism prominent in many myths. The other characters listed - Theseus, Hercules, and Achilles - are equally famous in Greek mythology but are known for different heroic feats: Theseus for his journey to Athens and overcoming the Minotaur, Hercules for his Twelve Labors, and Achilles for his prowess in the Trojan War.