Conspiracy theory and religion are complex phenomena. The relationship between them varies. This chapter introduces some of these relations, highlighting conspiracy theory in, about, and as religion. Conspiracy theory as religion highlights conspiracy thinking as worldview – conspiracism – and the parallels and differences between religion and conspiracism in modes of thinking and organizing collective action. Conspiracy theory in religion highlights religions as organized collectives, the content of and the roles more specific conspiracy theories play in different regions for different groups. Conspiracy theory about religion highlights the varied uses of conspiracy theories in demonizing religious collectives.