The mythical hero famous for rescuing Andromeda from a sea monster is Perseus. In Greek mythology, Perseus is the son of Zeus and is best known for his quest to slay Medusa and obtain her head. His journey to save Andromeda, who was to be sacrificed to a sea monster as punishment for her mother's hubris, highlights his bravery and heroism. Perseus ultimately defeats the monster and marries Andromeda, securing his legacy as a great hero in mythical lore.