The Twelve Olympians were the main gods of ancient Greek mythology who lived on Mount Olympus. They included Zeus, Hera, Poseidon, Demeter, Athena, Apollo, Artemis, Ares, Aphrodite, Hephaestus, Hermes, and either Hestia or Dionysus, depending on the source. Each god ruled over a specific aspect of the world, from the sea to the sun, love, war, and more.