This is a major revision (everything is new except for one section) of the Stanford Encyclopedia of Philosophy article on Pierre Bayle. There are new sections on "The Society of Atheists" and "Freedom of Conscience," as well as completely revised sections on "Skepticism", "Religious Toleration", and the "Bayle Enigma". From now on I will be the sole author of the article. Many thanks to Thomas Lennon for initially involving me in the project, and for handing it over to me.