With all due respect to T. S. Eliot, maybe the world really does end with a bang, not a whimper. Whether of our own creation (nuclear holocaust) or of nature’s (asteroid impact), plenty of cataclysms could doom civilization—perhaps even putting the survival of the species in jeopardy. We assessed the likelihood of several doomsday scenarios, from oft-discussed threats such as climate change to more fanciful ideas such as quantum fluctuations that would destroy our universe. The probabilities listed here are not scientific fact—an impossible goal when estimating the possibility of unprecedented events—but informed conjecture based on researchers’ expert opinions. We also relied on those opinions to approximate how catastrophic each event would be, ranging from 1 (localized chaos) to 10 (good-bye, universe).