If there is such a thing as God, I believe it to be the conglomeration of all rules and governance of existence. Things like gravitation toward mass, dissipation/entropy of energies, the interactions between atomic and sub-atomic particles, all the way up through the persistence of life. That is God. Not a being, not a consciousness, but an entity nonetheless. The strongest one in the universe. God is the rule you can't break. The realities by which we are able to and are forced to live under... that provide for us as well as hinder us.
And no, I'm not talking about science. Science doesn't govern these things, it only studies them, and is a man-made contrivance. Without conscious beings, there would be no science. And what I am talking about persists eternally beyond anything so minuscule as that. God is what is and has always been. No beginning, and never an end. God is existence.