The 12 Gods of Greek Mythology are the ones that

The twelve principal gods of Olympus are the principal deities among the gods traditionally worshipped in ancient Greek mythology. These gods were centered on Zeus and resided on Mount Olympus. Twelve of these gods, more important in comparison to the others, were known as the Twelve Principal Gods of Olympus. However, due to the fact that different gods were included within the twelve principal gods at different times, there were actually 14 gods who enjoyed this honor.

The story of the twelve principal gods of Olympus began to be written as early as the 6th century BC. And of these twelve main gods, ten must have appeared: Zeus, Hera, Poseidon, Mars, Hermes, Hephaestus, Aphrodite, Athena, Apollo and Artemis. Hestia was originally one of the twelve principal gods, but she gave up her position as principal god to Dionysus in order to live with mortals; Demeter had half a year in order to live with her daughter Persephone in the Underworld and would give up her position as principal god to Hades, the king of the underworld.

What earned the main gods of Olympus their supremacy among the gods was the combined efforts of Zeus and his brothers and sisters to defeat the titanic race of giants. Zeus and his siblings Hera, Poseidon, Demeter, Hestia, and Hades accounted for almost half of the twelve gods; most of the rest were the children of Zeus and other goddesses, with the exception of Athena, who grew out of Zeus's head, and Hephaestus, whom Hera produced on her own but who was also the child of both of them.