This chapter presents the concept of harm reduction (HR), which was developed in the 1980s in response to prevention issues related to the intravenous use of psychoactive substances. It became progressively integrated with the public health approach for addictive behaviours. In its current definitions, HR concerns the laws, programmes and practices principally aimed at reducing negative consequences associated with legal and illegal substance consumption, both in the health sector and socioeconomic levels, without necessarily reducing consumption itself. HR finds its legal grounding in constitutional and international law, particularly the international conventions on human rights. In terms of problem gambling, public policies have for a long time mirrored the efforts of operators as part of their corporate social responsibility, known generically as “responsible gambling”. This approach centres on providing information to players and applying limitation and exclusion measures. HR differs from “responsible gambling” in that it does not primarily focus on problem gambling, the preservation of interests of recreational players and the industry but on reducing the burden of problems upon society at-large and its citizens. This requires taking into account the conflict of interest resulting from the substantial contribution made by those who gamble excessively towards gambling revenue.