Tourism is a phenomenon that can provide numerous benefits, such as economic development, nature preservation, and intercultural understanding. However, the way we practice leisure travel is currently unsustainable. As well as generating carbon emissions that exacerbate the global climate crisis, tourism practices can degrade destination environments and perpetuate unequal power dynamics between different societies and cultures. Peripheral and developing nations like Greenland often rely on tourism for export revenue, job creation and social mobility. However, their peripheral or ‘frontier’ quality can contribute to a tourist imaginary that frames such places as empty landscapes for unregulated adventure. This is problematic because these destinations also tend to house fragile natural environments and marginalised local communities. This PhD thesis uses Greenland as a case study of a tourism destination ‘on the edge’, where tourism is an important industry, yet simultaneously triggers tensions on environmental, social, cultural and economic levels. The destination-level tensions created by tourism can partly be addressed by changing the in-destination behaviour of tourists. This is the focus of the current PhD thesis, which has an overarching aim of understanding and encouraging sustainable tourist behaviour. It does this through three independent but interlinked papers, each of which focuses on a distinct component of a theoretical framework for sustainable behaviour change. Paper 1 is concerned with understanding the context of sustainable tourist behaviour in Greenland, by taking an inductive approach towards exploring the varied interpretations of sustainable tourism among local industry stakeholders. Paper 2 shifts to the tourist perspective, employing a mixed-methods research design to uncover some of the psychological antecedents of (un)sustainable tourist behaviour. Paper 3, informed by findings from Papers 1 and 2, designs and tests a behavioural intervention to encourage a specific sustainable tourist behaviour in Greenland, and uses a survey experiment to reveal the psychological mechanisms driving this intervention. The thesis produces five overarching theoretical contributions that speak to different streams of literature within tourism and consumer behaviour. Firstly, the thesis nuances current thought around how sustainable tourism is conceptualised, exposing some of the pitfalls connected with existing framings and suggesting more appropriate ones. Secondly, the thesis contributes knowledge on the role of emotions as psychological antecedents of sustainable tourist behaviour, providing insights into how the constructs of gratitude and entitlement influence (un)sustainable tourist behaviour. The finding that the same psychological antecedent can have opposing influences on different types of sustainable behaviour leads to the third contribution: support for the use of the tourism context to advance knowledge on consumer behaviour, specifically sustainable consumer behaviour in hedonic contexts. The fourth contribution addresses literature on behaviour change, by revealing new and sometimes contradictory relationships between behavioural interventions and their determinants. Finally, the thesis demonstrates the relevance of a novel type of case in tourism –the extraordinary destination – which can be used to advance knowledge on the ‘WEIRD’ tourist segment and the future of extreme travel, while also addressing the urgent matter of the vulnerability of these types of destinations. On a practical level, the thesis provides concrete recommendations for destination managers, tourism operators, tourism marketing professionals, and managers of protected natural areas.