The Titans were an elder generation of gods who ruled the cosmos before the Olympian gods came to power. They were responsible for the original ordering of time and the establishment of fixed heavenly cycles.
The eldest of the Titans, Cronus and his four brothers, Crius, Coeus, Hyperion and Iapetus, were imprisoned in Tartarus by Zeus after he was victorious in the Titanomachy. Many of the younger Titan gods, however, allied themselves with Zeus and retained their divine rights under the new regime. Some of these allies later proved to be rebellious and were sentenced to harsh punishments, such as Atlas who was condemned to bear the heavens, and Prometheus, who was chained to a rock and an eagle set to feed on his liver.
The most important of the Titan gods were the twelve Uranids (Cronus, Oceanus, Iapetus, Hyperion, Crius, Coeus, Rhea, Tethys, Theia, Phoebe, Themis and Mnemosyne) and the four Iapetionids (Atlas, Prometheus, Epimetheus and Menoetius). Many of the children and grandchildren of the Titans also bore the name of Titan. These included the Hyperionids (Helius, Selene and Eos), the Coeids (Leto, Asteria and Hecate) and the Creionids (Pallas, Astraeus and Perses).