Mass mortality events (MMEs), the rapid, catastrophic die-off of organisms, are an example of a rare event affecting natural populations. Individual reports of MMEs clearly demonstrate their ecological and evolutionary importance, yet our understanding of the general features characterizing such events is limited. Here, we conducted the first, to our knowledge, quantitative analysis of MMEs across the animal kingdom, and as such, we were able to explore novel patterns, trends, and features associated with MMEs.