@mcurie If you are talking about THE God, then no one. How should one respond to the old schoolboy retort, “If everything needs a cause, who caused God?”

First, philosophers and theologians do not maintain that whatever exists needs a cause. Instead, they propose that certain things need causes, such as things that have a beginning or things that don’t have to exist.

If something came into existence at a certain point in time—that is, if it had a beginning—then there needs to be a cause, an explanation, for why it came to be. But if something exists outside of time—like God—then it does not need an explanation for its beginning, because it does not have one.

In the same way, if something doesn’t have to exist, then we need an explanation for why it does exist. But if something does have to exist—if it is a necessary being, like God—then it does not need a further explanation.

The things we perceive in the universe, including space and time themselves, appear to have had a beginning, and so they need a cause—a reason why they began in the first place.

In the same way, each particular bit of matter in the universe doesn’t seem to be necessary. Each could not exist. Therefore, we need an explanation for why each does exist.

Believing philosophers and theologians thus propose God as the ultimate explanation for these things. But since he is a necessary being that exists outside of time, he needs no further explanation.

Indeed, the question “Who created God?” is nonsensical, because it amounts to asking “Who created an uncreated being?”

He was always there, always has been, and always will be. He needs no explanation. He is the creater, he never had to be created.