[1] Its main source is in the parish of Great Bedwyn, Wiltshire and it flows 16 kilometres (10 mi) in a northeasterly direction into Berkshire.

It discharges into the Kennet at Hungerford,[2][3] which has a smaller average flow and width upstream of that point.

The Dun valley is an important transport route through the high chalklands between the London Basin to the east and the Vale of Pewsey to the west.

It is the route by which the Kennet and Avon Canal (linking London and Bristol) enters the Thames basin from the Vale of Pewsey, crossing the watershed with the aid of the Bruce Tunnel and Crofton Pumping Station.

[4] During or after the building of the Kennet and Avon Canal in the late 18th century, the Shalbourne was diverted into it.