Although ignorance has long played a critical off-stage role in anthropological discussions, controversies and theories about ritual and religion, it has only recently been cast under the analytical spotlight as an ethnographic topic in itself. Following a brief overview of the long-standing but largely implicit presence of ignorance in the anthropology of religion over the last century, this chapter explores three broad themes in the current literature on ritual and religious ignorance: loss, change and collective memory; the politics of ignorance; and ignorance as a strategic or ethical project. Rather than attempting to delineate a clear-cut category of ‘ignorance’, the chapter takes seriously its definitional ‘fuzziness’ as central to the real-world complexities with which anthropologists inevitably have to grapple. The ethnographies featured in the chapter have revolved around various modalities of ignorance—lost or forgotten memories, uncertainty, withheld knowledge, secrecy.