Polycystic Ovary Syndrome (PCOS) affects a significant number of women physically, psychologically, and socially. The main symptoms are abnormal or absent periods, fertility problems, insulin resistance, hirsutism, acne, and weight gain. The syndrome also increases the risk of developing type 2 diabetes (T2D), cardiovascular disease (CVD), obesity, obstructive sleep apnoea, depression, and endometrial cancer. Despite the recommendation for an active lifestyle being the cornerstone of treatment for PCOS, there remains several known and complex barriers to achieving this target.The aim of the research included in this thesis is to explore the lived experiences of women living with PCOS and overweight or obesity, and to develop and evaluate the feasibility of a novel intervention to increase physical activity and improve eudaimonic wellbeing (EWB) - a subtype of positive psychology encompassing self-acceptance, positive relations with others, purpose in life, personal growth, autonomy, and environmental mastery. An exploratory sequential study design was used with mixed methods and follows the Medical Research Council (MRC) framework for complex health interventions. The data collected in the separate studies used several approaches distinct in their focus and application but connected by the theme of positive psychology with the aim of helping women living with PCOS to flourish. First, a qualitative evidence synthesis (QES) explored the existing literature on the lived experience of women with PCOS and its impact on their wellbeing. Data were analysed by thematic synthesis (Thomas & Harden, 2008) which produced descriptive and analytical findings. The descriptive themes found that although there were various treatments for PCOS, many were deemed ineffective, had unwanted side effects, or were limited in availability. Information on self-management of PCOS from healthcare professionals was often deemed incomplete or irrelevant, with little advice on long term health risks and how they might be ameliorated. Analytical themes showed that elements of EWB could be impacted by the lived experience of PCOS, which has previously not been researched. Second, a qualitative study was undertaken using semi-structured interviews, with the interview schedule based on the findings of the evidence synthesis. The data were analysed using template analysis (King, 1998), through the specific lens of six eudaimonic elements. Findings suggested that the eudaimonic wellbeing of women living with PCOS was impacted both positively and negatively by the syndrome. Self-acceptance was affected by hirsutism, acne, and overweight; positive relationships with others was impacted by infertility and hirsutism; and personal growth was impacted by psychological distress.Third, findings from the evidence synthesis and qualitative study were used to develop a real-world physical activity and eudaimonic wellbeing intervention, for which a feasibility and acceptability study was completed. Alongside increased physical activity levels, the intervention incorporated eudaimonic wellbeing to explore its possible positive impact on the self-management of PCOS. The main findings were that the intervention as designed was not feasible mainly due to recruitment issues, but also due to challenges with the fidelity of the online intervention. However, it was acceptable to the participants, who in post-intervention interviews expressed the positive benefits they experienced during and immediately after the intervention, including improved overall sense of wellbeing, improved coping strategies, and the knowledge that they were not the only ones living with PCOS.In summary, the original contribution to knowledge is that EWB can be related to the lived experience of PCOS. Further, by participating in a novel physical activity intervention which incorporates eudaimonia, the concepts can be learnt and applied to help support women living with PCOS to better self-manage their syndrome daily. This thesis also highlights feasibility issues with the intervention and suggests changes to optimise the design and conduct of future studies.