The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about 65.5 to 56 million years ago (65.5 ± 0.3 to 55.8 ± 0.2 Ma). It is the first epoch of the Palaeogene Period in the modern Cenozoic Era. As with most other older geologic periods, the strata that define the epoch's beginning and end are well identified but the exact date of the end is uncertain.
The Paleocene Epoch immediately followed the mass extinction event at the end of the Cretaceous, known as the K-T boundary (Cretaceous - Tertiary), which marks the demise of the dinosaurs (except their descendants, modern birds) and much other fauna and flora. The die-off of the dinosaurs left unfilled ecological niches worldwide, and the name "Paleocene" comes from Greek and refers to the "old(er)" (παλαιός, palaios) – "new" (καινός, kainos) fauna that arose during the epoch, before modern mammalian orders emerged in the Eocene.