The Overthrowing of Ouranus was a mythological conflict between Ouranos and five of his sons.
Ouranos and Gaia had twelve sons and six daughters. The eldest, the Cyclopes and Hekatonkheires inside the Earth. Gaia suffered pain and persuaded her Titan sons to rebel. Four of these were set as sentinels at the four corners of the world, ready to grasp their father as he descended to lie upon the Earth, Coeus at the North, Hyperion at East, Iapetos West and Krios South. The fifth, Kronos, took his place in the centre, and armed with an adamantine sickle, castrated Ouranos while his brothers held him firm. The sky-god's blood fell and drenched the earth, producing the Erinyes the Gigantes and the Meliai. The severed genitalia which landed in the sea, impregnating Thalassa giving birth to Aphrodite 
After his downfall, Ouranos prophesied the fall of the Titans - the punishment they would suffer for their crime.