The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/Series.
The stage is named after the small river Rupel in Belgium, a tributary to the Scheldt.
The name Rupelian was introduced in scientific literature by Belgian geologist André Hubert Dumont in 1850.
The separation between the group and the stage was made in the second half of the 20th century, when stratigraphers saw the need to distinguish between lithostratigraphic and chronostratigraphic names.
The transition with the Chattian has also been marked with a GSSP in August 2017 (Monte Conero, Italy).