The Namurian is a stage in the regional stratigraphy of northwest Europe, with an age between roughly 331 and 319 Ma (million years ago).
It is a subdivision of the Carboniferous system or period, as well as the regional Silesian series.
The Millstone Grit Group in the lithostratigraphy of northern England and parts of Wales is also of Namurian age.
It is preceded by the Visean stage/age (which corresponds to the upper Carboniferous Limestone of Great Britain) and succeeded by the Westphalian stage/age (which corresponds to the lower and middle Coal Measures of Great Britain).
In the official geologic timescale of the International Commission on Stratigraphy (ICS), the Namurian straddles the boundary between the Mississippian subperiod (359-323 Ma) and the Pennsylvanian subperiod (323-299 Ma).