Marking Holocaust Remembrance Day on 27 January, this lecture will focus on the status of genocide denial, working through a number of 20th and 21st century genocides. Industries of denial spring up to counter the claims of victims of ethnic cleansing and genocide. The deniers or revisionists could be treated as other eccentric authors have, like quirky conspiracy theorists. However, there seems to be something more sinister, more demanding of our attention, which requires a special attitude to its proponents. This lecture will move through a discussion of the ethical grounds for the special category of genocide as a political crime and its relation to human rights.