Does the occurrence of a natural disaster such as an earthquake, volcanic eruption, tsunami, flood, hurricane, epidemic, heat wave, and/or plague increase the risk of violent civil conflict in a society? This study uses available data for 187 political units for the period 1950–2000 to systematically explore this question that has received remarkably little attention in the voluminous literature on civil war. We find that natural disasters significantly increase the risk of violent civil conflict both in the short and medium term, specifically in low- and middle-income countries that have intermediate to high levels of inequality, mixed political regimes, and sluggish economic growth. Rapid-onset disasters related to geology and climate pose the highest overall risk, but different dynamics apply to minor as compared to major conflicts. The findings are robust in terms of the use of different dependent and independent variables, and a variety of model specifications. Given the likelihood that rapid climate change will increase the incidence of some types of natural disasters, more attention should be given to mitigating the social and political risks posed by these cataclysmic events.