The Pantheon is a temple in Rome dedicated to all the Gods of the Roman people. In modern usage the word Pantheon has come to describe the family of Gods itself. For example the Greek Pantheon consists of the twelve Olympian Gods and various Titans and Chthonic deities associated with ancient Greek religion. The Celtic Pantheon consists of various Gods associated with Celtic Lore and so on.
Some Pagans believe that all Pantheons are basically the same group of Gods and Goddesses called by different names and given different characteristics based on the language and customs of different areas. Others believe that each cultural group has its own Gods and Goddesses who may have been cultural ancestors or tutelary spirits to that group’s ancestors. Still, others believe that there is only one God and one Goddess and that all the other Gods and Goddesses are different aspects or facets of these and yet still others believe that there is only one God/dess with both male and female qualities and all the Gods and Goddesses are His/Her many faces.
It is a matter of some debate among Pagans as to whether it is appropriate to “mix Pantheons”. That is to honor Gods and Goddesses from different families or cultural backgrounds at the same time. Some believe it is very rude or at the very least confusing to honor for example an Egyptian Goddess and a Gaulish God at the same ritual while others find this perfectly acceptable. Some believe that each individual or group should pick one Pantheon and honor only the Gods associated with that Pantheon at all gatherings while others believe it is appropriate to honor Gods from different Pantheons on different occasions, provided they are not called upon on the same occasion. However, practicality dictates that if an individual attends public festivals or celebrate feast days with other Pagans, some Pantheon mixing is bound to happen.