The Paleogene Period was a time of extremes and transitions. Bounded by the mass extinction at the end of the Cretaceous and the rise of modern grasslands, the climate of the Paleogene was globally much warmer than today’s, yet continents and ocean basins had nearly modern configurations and supported biotic communities and biogeochemical regimes of broadly familiar types. The causes, dynamics and functioning of the Paleogene Earth-Life System are being studied by an international and highly interdisciplinary group of scientists including paleontologists, geologists, geochemists, paleoceanographers, climate scientists, and ecologists, among others. This community is united by its curiosity about the Paleogene Earth and what its history can tell us about our future.