Overtourism has reemerged as a pressing issue in the wake of the COVID-19 pandemic, fuelling widespread public protests. Despite its growing relevance, the concept remains ambiguously defined in academic discussions. This study seeks to clarify the notion of overtourism by adopting a resident-centered perspective, emphasizing the economic, demographic, and socio-cultural factors that influence how the phenomenon is perceived. Focusing on Barcelona and employing a mixed-methods approach, the research reveals that residents primarily associate overtourism with excessive crowding, security concerns, pollution, and rising costs and gentrification. Through surveys of Barcelona residents and expert interviews, the study finds that millennials are the most critical of overtourism, a stance shaped by their lower economic reliance on tourism, political ideology, and higher education levels.