Mythology and religion are completely different things.

There is Greek religion (sacrifices, festivals, laws) and Greek mythology* (Prometheus and fire, Trojan War, Pandora's box). There is Christian religion (church, Ten Commandments, prayer) and Christian mythology* (Genesis creation, Noah's flood).

*I would like to note that it is not my intention at all to offend by using the word "mythology". In fact, unlike some others, I do not hold the word to have any negative connotation implying false belief. Think of my use of "mythology" as "etiological story" which naturalistic explanations would also be.