Overtourism is the increase in tourist numbers at such high volumes that it negatively impacts local residents, visitors, and the surrounding environment of a particular destination. The actual number of visitors is subjective to the capacity a given destination can manage without seeing detriment to their environment.

Overtourism occurs when the number of visitors to a destination becomes so high that it negatively impacts the quality of life for residents and the experience for the tourists themselves. Environmentally, it leads to the degradation of natural ecosystems, increased waste, and the depletion of local resources like water and energy. Socially, it often causes the "displacement" of local populations as housing prices and rents are driven up by short-term holiday rentals like Airbnb. It can also lead to the loss of a destination's cultural identity, as small, local shops are replaced by generic tourist traps and the "Disneyfication" of historic neighborhoods occurs. In extreme cases, it creates "hostility" between residents and travelers, as seen in cities like Venice or Barcelona. Ultimately, overtourism threatens the long-term sustainability of the very locations people want to see, leading to closures (like Maya Bay in Thailand) or the implementation of strict daily visitor caps.