Recent years have seen a renewed interest in energy amongst International Relations (IR) scholars. The existing IR literature is characterised by a debate between a realist-inspired ‘geopolitical’ approach that sees energy as a source of zero-sum conflict, and a liberal-influenced ‘global energy governance’ approach which emphasises interdependence and cooperative dynamics. However, by adopting a systemic perspective these IR approaches fail to account for the full range of political dynamics shaping inter-state energy relations. This article consolidates insights from the broader literature on energy politics to develop a new securitisation approach to international energy politics. It argues that energy securitisation – a process where governments frame energy as an existential threat to state interests – is variable and contingent. It occurs in states where energy issues are implicated in economic, regime and/or geopolitical security concerns, and leads governments to adopt nationalistic policy frameworks that result in international conflicts over energy. The utility of this securitisation approach is illustrated with a case study of the divergent energy behaviour of two major energy exporters (Russia and Australia). By accounting for domestic and international dynamics, and explaining rather than assuming the securitisation of energy, this securitisation approach offers more explanatory purchase than existing IR energy theories.