Rhea, in Greek religion and mythology, a Titan. She was the wife and sister of Kronos, by whom she bore Zeus, Poseidon, Pluto, Hestia, Hera, and Demeter. She eventually helped Zeus overthrow Kronos. Her worship, which was orgiastic and associated with fertility rites, was particularly prominent in Crete. The Greeks often identified her with Gaea and Cybele. In Rome, Rhea was worshiped as Magna Mater and identified with Ops. See Great Mother Goddess.