In ancient Greek religion and mythology, the twelve Olympians are the major deities of the Greek pantheon, commonly considered to be Zeus, Hera, Poseidon, Demeter, Athena, Apollo, Artemis, Ares, Hephaestus, Aphrodite, Hermes, and either Hestia or Dionysus. They were called Olympians because, according to tradition, they resided on Mount Olympus.
Although Hades was a major ancient Greek god and was the brother of the first generation of Olympians (Zeus, Poseidon, Hera, Demeter, and Hestia), his realm was the underworld, far from Olympus, and thus he was not usually considered to be one of the Olympians.
Besides the twelve Olympians, there were many other cultic groupings of twelve gods.
The Last Olympian
(Percy Jackson and the Olympians #5)
Rick Riordan
All year the half-bloods have been preparing for battle against the Titans, knowing the odds of victory are grim. Kronos's army is stronger than ever, and with every god and half-blood he recruits, the evil Titan's power only...
The Battle of the Labyrinth
(Percy Jackson and the Olympians #4)
Rick Riordan
Percy Jackson isn't expecting freshman orientation to be any fun. But when a mysterious mortal acquaintance appears at his potential new school, followed by demon cheerleaders, things quickly move from bad to worse...
The Titan's Curse
(Percy Jackson and the Olympians #3)
Rick Riordan
It's not everyday you find yourself in combat with a half-lion, half-human.
But when you're the son of a Greek god, it happens. And now my friend Annabeth is missing, a goddess is in chains and only five half-blood heroes can...
The Sea of Monsters
(Percy Jackson and the Olympians #2)
Rick Riordan
After a year spent trying to prevent a catastropic war among the Greek gods, Percy Jackson finds his seventh-grade school year unnervingly quiet. His biggest problem is dealing with his new friend, Tyson--a six-foot-three...
The Lightning Thief
(Percy Jackson and the Olympians #1)
Rick Riordan
Percy Jackson is about to be kicked out of boarding school... again. And that's the least of his troubles. Lately, mythological monsters and the gods of Mount Olympus seem to be walking straight out of the pages of Percy's...