Polytheism means believing in many gods. A person that believes in polytheism is called a polytheist. A religion with polytheism can be called a polytheistic religion.
Polytheism is well documented in historical religions of classical antiquity, especially Ancient Greece and Ancient Rome. Other ancient people who were polytheists include Germanic paganism, Ancient Egypt, the Celts and the Norse.
Polytheism for Kids. Kiddle Encyclopedia.