Mass gatherings include a diverse range of events such as sporting competitions, religious ceremonies, entertainment activities, political rallies and cultural celebrations, which have important implications for population well-being. However, if not managed properly, these events can amplify health risks including those related to communicable diseases, and place undue strain on health systems in host countries and potentially in attendees' home countries, upon their return. The coronavirus disease 2019 (COVID-19) pandemic has provided a unique opportunity to evaluate the risk factors associated with mass gatherings and the effectiveness of applying mitigation measures during infectious disease emergencies. The pandemic has also allowed event organizers and health officials to identify best practices for mass gathering planning in host countries. To guide decisions about whether to hold, postpone, modify or cancel a mass gathering during the COVID-19 pandemic, the World Health Organization and its partners developed normative guidance and derivative tools promoting a risk-based approach to mass gathering planning. This approach involves three steps to guide decision-making around mass gatherings: risk evaluation, risk mitigation and risk communication. The approach was applied in the planning and execution of several mass gathering events, including the Tokyo 2020 and Beijing 2022 Olympic and Paralympic Games. Lessons identified from these large-scale international events offer insights into the planning and implementation of mass gathering events during a pandemic, and the broader impacts of such events on society. These lessons may also further inform and refine planning for future mass gatherings.