Greek religion encompasses the collection of beliefs and rituals practiced in Ancient Greece in form of cult practices. It is therefore the practical counterpart of Greek mythology. Within the Greek world, religious practice varied enough so that one might speak of Greek religions. The cult practices of the Hellenes extended beyond mainland Greece, to the islands and coasts of Ionia in Asia Minor, to Magna Graecia (Sicily and southern Italy), and to scattered Greek colonies in the Western Mediterranean, such as Massalia (Marseille). Greek examples tempered Etruscan cult and belief to inform much of the Roman religion.

There is a scholarly belief that early Greek religion came from, or was strongly influenced by, shamanistic practices from the steppes of Central Asia to the Greek colony of Olbia in Scythia, on the northern shore of the Black Sea, then all the way down to Greece.