The last decade has seen a number of extreme wildfire events around the globe – from the Canberra and wider Alpine fires in Australia in 2003, to the recent spate of wildfires in the United States. Ongoing research into dynamic fire propagation and extreme fire weather events has provided a number of insights into the processes that cause such fires to develop, and which contribute to their most devastating impacts. In this presentation, a number of the latest insights into the causes of dangerous and unexpected fire spread will be reviewed and their role in driving extreme wildfire development and impacts will be illustrated in a number of case studies from southeastern Australia and the United States.