Unstable geological conditions and steep topography, combined with frequent extreme weather conditions, make the Hindu Kush-Himalayan (HKH) region prone to many natural hazards. Among these, flash floods – severe flood events that occur with little warning – are particularly challenging for communities, threatening lives, livelihoods, and infrastructure. Vulnerable groups such as the poor, women, children, the elderly, and people with disabilities are often the hardest hit. This Training of Trainers Manual is designed to help build the capacity of trainers in flash flood risk management, who can then disseminate the knowledge to a larger number of practitioners. The manual presents an eight-day course including a three-day field trip. Detailed lesson plans for 21 sessions are followed by resource materials that will enable the trainers to replicate the course in their own work areas. Designed for participants with a basic knowledge of flash flood risk assessment and management, the manual focuses on developing understanding of the types, causes, and impacts of flash floods; flash flood hazards, vulnerability, risk assessment, and management methods; the role of local knowledge and gender perspectives in flash flood risk management; participatory social hazard mapping techniques; concepts and methods for an integrated approach to flash flood risk management; the full range of risk management measures for specific types of flash floods; legal and institutional aspects; and modelling tools. It is hoped that the publication will contribute meaningfully towards reducing disaster risk and providing greater physical security for the people of this vulnerable region.