Back during the ancient times, the ancient Greeks used to worship a lot of Gods and Goddesses, most especially the Olympians: they were a group of deities who called the top of a mountain their home and ruled over Greece. The names of the main gods were Zeus, Hera, Poseidon, Hades, Athena, Apollo, Artemis, Ares, Hermes, Hephaestus, Aphrodite, Dionysus, Hestia, and Demeter.

(Thankfully, she hasn't lose knowledge on Greek mythology in school despite just having into the land of her ancestors recently.)

Nowadays though, many modern Greeks just worship one God and many other countries have practiced other religions throughout my world's history as well.