Background: Over-tourism—characterized by excessive tourist concentration leading to congestion, environmental degradation, and cultural disruption—has emerged as a major threat to UNESCO World Heritage Sites. These sites face increasing pressure due to global tourism growth, cheap transportation, and poor regulatory frameworks.

Objective: This study examines the drivers, impacts, and management strategies of over-tourism in UNESCO sites, drawing evidence from global case studies to propose sustainable management frameworks.

Methods: A qualitative comparative analysis was conducted across five UNESCO sites: Venice (Italy), Machu Picchu (Peru), Angkor Wat (Cambodia), Santorini (Greece), and Kathmandu Valley (Nepal). Data were collected using 38 stakeholder interviews, policy document reviews, tourist surveys (n = 280), and site observations. Thematic coding and policy analysis identified key drivers and mitigation strategies.

Results: Over-tourism led to increased environmental degradation, rapid commercialization, housing displacement, and physical erosion of monuments. Sites with strong visitor caps, controlled ticketing, community participation, and zoning regulations exhibited improved sustainability outcomes. Digital management tools (e-ticketing, AI-based crowd forecasting) significantly reduced congestion.

Conclusion: Effective management of over-tourism requires integrated strategies combining governance reforms, technological tools, community engagement, and sustainable visitor regulation.