In Greek myth, Zeus was the ruler of the gods of Mount Olympus as well as the god of storms and lightning. The son of Cronus and Rhea, Zeus was the only child of the leader of the Titans who avoided being devoured. Raised in seclusion, Zeus eventually freed his sibling deities and defeated his father, becoming leader of the Greek gods and marrying his sister Hera, having many children with her (including Hephaestus and Ares).
Zeus was infamous for his infidelity, taking a myriad of forms to have affairs with females (mortal and immortal, human and other animals) and having numerous illegitimate children, such as Heracles. Zeus is frequently depicted as a powerful man with long hair and a bushy, curly beard.
The Romans knew him as Jupiter.
Zeus also exists, in largely identical form, in the Amalgam universe.