Read Aristotle - NICHOMACHEAN ETHICS - One must be virtuous [ethical] in order to live a happy life... No God required.
Or the Kantian categorical imperative. Fifteen minutes of googling would have told the questioner everything he might have wanted to know about this, but of course that's not the point here.
Aristotle fed off Plato's values which were downright theistic. Aristotle failed to establish First Causes of his values apart from Plato, which is why modernists pretty much ignore the poor guy except to trod him out when he serves their purpose.