The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/Series.
The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage of the Miocene).
An official GSSP for the Chattian Stage was ratified in October of 2016.
The top of the Chattian Stage (which is the base of the Aquitanian Stage, Miocene Series and Neogene System) is at the first appearance of foram species Paragloborotalia kugleri, the extinction of calcareous nanoplankton species Reticulofenestra bisecta (which forms the base of nanoplankton biozone NN1), and the base of magnetic C6Cn.2n.
The Chattian is coeval with regionally used stages or zones such as the upper Avernian European mammal zone (it spans the Mammal Paleogene zones 30 through 26 and part of 25[8]); the upper Geringian and lower Arikareean mammal zones of North America; most of the Deseadan mammal zone of South America; the upper Hsandgolian and whole Tabenbulakian mammal zone of Asia; the upper Kiscellian and lower Egerian Paratethys stages of Central and eastern Europe; the upper Janjukian and lower Longfordian Australian regional stages; the Otaian, Waitakian, and Duntroonian stages of the New Zealand geologic time scale; and part of the Zemorrian Californian stage and Chickasawhayan regional stage of the eastern US.