Criticism of religion involves criticism of the validity, concept, or ideas of religion. Historical records of criticism of religion go back to at least 5th century BCE in ancient Greece, in Athens specifically, with Diagoras "the Atheist" of Melos. In ancient Rome, an early known example is Lucretius' De rerum natura from the 1st century BCE.

Abū al-ʿAlāʾ al-Maʿarrī was a philosopher, poet, and writer from Ma'arrat al-Nu'man, Syria. Because of his controversially irreligious worldview, he is known as one of the "foremost atheists" of his time according to Nasser Rabbat.