Viewed from the perspective of the global history of modern atheism, Germany stands out for its contribution to three distinct varieties: the theoretical atheism promulgated by philosophers and cultural critics between the late Enlightenment and the interwar period; the mass atheism that has grown with religious indifference since the late twentieth century; and the secularist atheism embedded within popular anticlerical movements between the middle of the nineteenth and the middle of the twentieth centuries. Whereas the first two varieties of atheism have been the subject of extensive study, the third has received less scrutiny. Yet, arguably secularist atheism had the greatest impact on the course of modern German religious and political history. In order to make this case, this chapter will summarize the histories of theoretical and mass atheism and then focus on the dynamics and developments of secularist atheism.