Résumé : This thesis is about a study-case on Extinction Rebellion’s acts of civil disobedience and their place in a democracy. An extensive analysis on Extinction Rebellion’s emergence was made and the context of its appearance. In order to understand how civil disobedient acts take place in a democracy, in XR’s case, we have studied its internal and external structure, its core values and the way the movement protests. This allowed us a better comprehension of Extinction Rebellion given its atypical structure, precise objectives, and a radical method of action.Before going in a more in-depth analysis of Extinction Rebellion’s acts of civil disobedience, a detailed analysis of the context around the movement was crucial. Therefore, we have seen that the structure of Extinction Rebellion is composed of three characteristics: civil disobedience, non-violence and climate and ecological urgency. The in-depth study of Extinction Rebellion’s structure allowed a better understanding of the movements choice of using civil disobedient acts. Afterwards, we have examined the events that took place in October 2018 and how it lead to the declaration of environmental and climate emergency in the UK. This study was organized in two parts: a discourse analysis and interviews, both qualitative methods. These methods allowed us to have both an internal and external point of view of the movement’s civil disobedient acts and how they are seen. Therefore, the legitimacy of these actions could be assessed through this analysis.In our literature review we assessed and defined democracy and civil disobedience, other aspects have also been analyzed, like citizens assemblies, non-violence, etc. All of these aspects helped us answer our question, on how civil disobedient acts of Extinction Rebellion from October 2018 affected the UK’s democracy.