Abstract: The Middle Pleistocene stage in the International Chronostratigrahic Chart has been ratified as Chibanian. Its time interval is from 0.774 Ma to 0.129 Ma. Lower boundary of this stage corresponds to the MIS 19 (marine isotope stage - 19) and also palaeomagnetic polarity reversal of Matuyama-Brunhes. The data source and locality are the Chiba section (Japan). Based on investigation in detail and dating by different methods of the marine Chiba deposits, the relevant section has been adopted as the stratotype section and type locality of the Chibanian stage in January 2020. Chiba section is now an international geosite and geological heritage.