Extreme wildfires events (EWEs) represent a minority among all wildfires but are a true challenge for societies as they exceed the current control capacity even in the best prepared regions of the world and they create destruction and a disproportionately number of fatalities. Recent events in Portugal, Chile, Greece, Australia, Canada, and the USA provide evidence that EWEs are an escalating worldwide problem, exceeding all previous records. Despite the challenges put by climate change, the occurrence of EWEs and disasters is not an ecological inevitability. In this chapter the rationale of the definition of EWEs and the integration of potential consequences on people and assets in a novel wildfire classification scheme are proposed and discussed. They are excellent instruments to enhance wildfire risk and crisis communication programs and to define appropriate prevention, mitigation, and response measures which are crucial to build up citizens safety.