Blackmail is a term that is widely known through fiction and popular culture as an illegal means of gaining money or leverage by threats to reveal knowledge. Criminologically and legally, however, its meaning is contentious, reflected in how it has different meanings in different jurisdictions. Definitions are contested: there is an underlying debate about whether it should be seen as a criminal or moral offence; and furthermore, if seen as criminal, distinctions between blackmail and other crimes (e.g. extortion) are not always clear. International data is hard to compare because its collection reflects these differences of viewpoint and meaning. Data sources exist but tend to encompass extortion as well as blackmail. Popular representations of blackmail are illustrative of ‘reputational’ blackmail and contempt for blackmailers.