Kronos (also Cronos or Cronus) is a Titan in Greek mythology. He is the Titan of time. His parents are Gaia (the Earth) and Uranus (the sky). Uranus was very vain and he cast the Cyclops and hundred handed ones into Tartarus (a deep pit), but Gaia wanted all her children to live in peace so she told the Titans to kill Uranus and she gave them a sharp scythe, which Kronos took. While Kronos's brothers held the sky he slashed it open with the scythe and he became lord of the universe, but he had too much of his father in him so he kept his brothers locked in Tartarus.
With his sister and wife Rhea his children are Demeter, Hades, Hera, Hestia, Poseidon, and Zeus. Kronos became so angry about his children's power, and had been warned by Gaia, or mother earth, that one of his children would overthrow him. Because of this, he decided to eat them so he could obtain their power and stop the risk of the end of his reign. He ate all but Zeus because Rhea hid baby Zeus and gave Kronos a rock instead. Later, when Zeus was grown, he fed Kronos a mixture of mustard and wine and made him throw up his children. The reason they all survived in Kronos's stomach was because they were gods and goddesses, they were immortal.
Zeus and his siblings were angry and Kronos was angry as well, they started the great war among the Titans and the gods. No one was winning the war and no one was losing, so Zeus asked Rhea for help. Rhea suggested they free the other Titans, whom Kronos locked away because they were too dangerous. The Titans were so happy to be freed from Tartarus, they helped Zeus win the war. Afterwards the other Titans thought they should have some power, but Zeus became head of the gods. The Titans refused to help Zeus further and planned revenge, only to fail against the all mighty Zeus.
After the war against the Olympians Zeus stole Kronos's scythe and cut him in small pieces and spread him across Tartarus (the lowest place in the Greek underworld) to dwell forever, but since Kronos was also immortal he lay in the deepest part of Tartarus waiting to be freed and have revenge on his sons. In some ways of telling he was later freed and became ruler of Elysian Islands.
In popular culture
Kronus is also mentioned in the series of the Percy Jackson books, depicted as the powerful, evil titan.
Kronos Facts for Kids. Kiddle Encyclopedia.