Religion

In the world of One Piece it is unknown whether the entity known as God truly exists, yet there are many religious references scattered across the series. In Skypiea, this title refers to the ruling body of sky islands, instead of any kings or other form of government, God is usually looked at as the ruler. This person however is not a real God but a physical being who is not all powerful and not perfect. Smoking God was the oldest known God 400 years ago, and Gan Fall was the previous God 6 years ago, before Enel took over. Enel took this title seriously, believing to be an all-powerful God only to be beaten up by Luffy. After Enel was gone, Gan Fall reclaimed the title.

Does God exist in One Piece?
Sanji has made many references of a possible God. In Loguetown, after lightning struck the scaffold Luffy was on and saved him from Buggy, Sanji asked Zoro of his beliefs, though Zoro didn't answer. During the Skypiea arc, Zoro claimed he never prays to God and doesn't care whether one exists or not. After defeating Jyabura of the CP9, Sanji mentions God again, saying "God creates food, and the Devil creates seasonings".

However, Conis questions if whether or not God exists, she then shouts out "Help us, God!!".

Bartholomew Kuma has a Bible in his hands and always carries it with him. Gecko Moria wears a cross around his neck, Mihawk also has weapons modeled after crucifixes, so the Shichibukai might be a Holy organization, considering the fact that the privateers they are modeled after were also a very Holy people. On the other hand while the city of Arabasta looks like a middle eastern land, their graveyards are cross shaped as well.

Trivia

 * In Oda's 1993 one-shot God's Gift for the Future prior to One Piece, "God" appears as a comical old man who isn't omnipotent at all, although he's perhaps supposed to be the real deal.