River Medway, river, southeastern England, rising in the heart of The Weald region and flowing 70 miles (110 km) to its North Sea mouth in the Thames at Sheerness, county of Kent. It makes a gap through the ridge south of Maidstone and a larger one through the North Downs between Maidstone and Rochester, where meanders abut against paper mills and cement works. The drowned lower portion 12 miles (20 km) below Rochester forms a tidal estuary navigable by shallow seagoing vessels.