This conceptual paper explores the use of psychology, especially positive psychology, to inform the design of travel experiences for a specific health outcome À enhanced participant wellbeing or mental health. It extends the concept of sustainable tourism as a tool for local, regional and societal improvement. Mental health is a growing issue in many developed countries: 30% of Australians report depressive symptoms, with implications for social sustainability. The paper reviews how positive psychology seeks to combine hedonic, eudemonic and social wellbeing into the integrated concept of "flourishing", creating positive emotions, engagement, and meaning. It uses the charity challenge model to explore tourism experiences that enhance participant wellbeing. Charity challenges are participatory, group travel events combined with extended physical activity, awareness-raising, and fund-raising for charity. These events inherently combine recognised pathways to wellbeing, e.g. being active, doing something meaningful, giving, and connecting with others. Other principles from positive psychology, such as intentional and volitional activity, goal attainment, activation of signature strengths, experiencing positive emotions/gratification, and capitalisation on positive experiences, can be incorporated into the event design to foster wellbeing outcomes. The paper suggests how this design might take shape, as well as management implications and further research questions.