Taken from GotQuestions.org
Question: “Who created God? Where did God come from?”
Answer: A common argument from atheists and skeptics is that if all things need a cause, then God must also need a cause. The conclusion is that if God needed a cause, then God is not God and if God is not God, then of course there is no God. This is a slightly more sophisticated form of the basic question “Who made God?” Everyone knows that something does not come from nothing. So, if God is a “something,” then He must have a cause, right?The question is tricky because it sneaks in the false assumption that God came from somewhere and then asks where that might be. The answer is that the question does not even make sense. It is like asking, “What does blue smell like?” Blue is not in the category of things that have a smell, so the question itself is flawed. In the same way, God is not in the category of things that are created or caused. God is uncaused and uncreated—He simply exists.How do we know this? We know that from nothing, nothing comes. So, if there were ever a time when there was absolutely nothing in existence, then nothing would have ever come into existence. But things do exist. Therefore, since there could never have been absolutely nothing, something had to have always been in existence. That ever-existing thing is what we call God. God is the uncaused Being that caused everything else to come into existence. God is the uncreated Creator who created the universe and everything in it.