Mass tourism has become a defining challenge for some of the world's most celebrated destinations, where the economic benefits of large visitor numbers are increasingly offset by the social, cultural, and environmental costs borne by local residents. Understanding these costs in detail is the starting point for designing effective responses. The negative effects of mass tourism on local communities operate across several dimensions. In cities and coastal areas that have become globally popular through social media exposure, property prices and rents rise sharply as short-term holiday rental platforms convert residential housing into visitor accommodation, displacing the communities that give these places their authentic character. Local infrastructure — transport, water supply, waste management, and medical services — is designed for the resident population and routinely overwhelmed during peak tourist seasons, degrading daily life for people who live there year-round. Cultural erosion is a subtler but equally damaging consequence: when a neighbourhood's economic survival depends on serving visitors rather than residents, local businesses, traditions, and social patterns gradually transform to meet tourist expectations rather than authentic local life, hollowing out the very character that made the destination appealing in the first place. Governments and tourism authorities have a range of management tools available. Visitor number caps for the most fragile heritage sites and natural areas, enforced through timed ticketing and booking systems, prevent the physical degradation that uncontrolled footfall causes. Tourist taxes — levied per visitor per night and ring-fenced for local infrastructure investment and affordable housing provision — distribute the economic burden of tourism more fairly across the community. Actively promoting off-peak travel and less-visited destinations through targeted marketing disperses tourism pressure more evenly across time and geography. When these measures are implemented consistently, mass tourism can be transformed from a threat into a genuinely sustainable economic asset for local communities.