Light festivals have evolved from their first editions in 1990 to become complex cultural and touristic phenomena on a global scale. These events integrate cultural and tourism promotion strategies, generating economic, cultural, and social benefits in the host cities. However, the existing literature is predominantly economistic in nature, focusing on the study of economic impacts and neglecting the study of actors, contexts, processes, interests, and motivations. This sociological research adopted a multi-sited critical ethnographic approach, complemented by statistical analysis and documentary analysis. The study focuses on the Portuguese festivals Lumina (Cascais, 2013-2018) and Luza (Loulé, 2017/8). The fieldwork was conducted between 2016 and 2021. This methodology allowed the researcher to explore in depth the interests and motivations for the realisation, visitation, and participation in the festivals of light by their main actors. This thesis concludes with a reflection on the instrumentalisation of these festivals in municipal politics and the need for evaluation criteria beyond the tangible. It also reviews the processes of artification carried out by festival directors to legitimise and revalue their programmes in the face of their financial precariousness and subordination to local powers. This work contributes significantly to urban sociology, the sociology of culture and the arts, and offers a critical perspective on light festivals in the contemporary context.