This book studies the different forms of religious disbelief in Ancient Greece, from impiety to atheism. It focuses mainly on atheism (both criticism of the Olympian gods and the questioning of the very idea of divinity). It is a historical study that begins with the pre-Socratic philosophers and ends with the appearance of Christianity and its debate with paganism. Special importance is given to great figures such as Socrates or philosophical movements such as Epicureanism.