Who was the ruler of the greek gods and goddesses before Zeus?

Before Zeus, the ruler of the Greek gods and goddesses was Cronus. Cronus, a Titan, overthrew his father Uranus and took control of the cosmos. However, he was later overthrown by his own son, Zeus, who led the Olympian gods in a rebellion against the Titans. This marked the transition of power from the Titans to the Olympian gods.