The United Nations Office for Disaster Risk Reduction (UNDRR) defines a disaster as a severe disruption of the functioning of a community or society resulting from hazardous events interacting with conditions of exposure, vulnerability, and capacity. This disruption leads to various losses and impacts, including human, mate- rial, economic, and environmental. The combination of vulnerability, hazards, and inability to reduce the potential negative consequences (of risk) results in disaster. Risk is the combination of the likelihood of an event and its negative consequences, which impact human life and infrastructure or may be defined as a degree of uncer- tainty resulting in potential loss (human-financial). Disasters can be broadly catego- rized based on the origin of the triggering event: natural disasters, anthropogenic disasters, and cascading disasters. Natural disasters include geophysical, meteo- rological, hydrological, climatological, and biological disasters. Anthropogenic or human-caused disasters include technological, complex emergencies, and environ- mental disasters. Cascading disasters include those disastrous events that occur when one initial event triggers a chain reaction of subsequent disasters. The chapter also discusses frameworks of “Disaster Risk Reduction” like the Sendai Framework for Disaster Risk Reduction (2015-2030), Sustainable Development Goals (SDGs), International Charter on Space and Major Disasters, Global Platform for Disaster Risk Reduction (GPDRR), and Regional DRR Frameworks. The chapter provides a brief but clear picture of disasters in general and natural disasters in particular, along with a thematic briefing of the chapter’s subject matters included in the book.