The Vale of Holmesdale is a comparatively narrow valley lying at the foot of the North Downs in Surrey and Kent, England. It is a relatively recent term compared to the many historic towns and villages that are in it. It stretches from Sugar Loaf Hill in Folkestone on the Kent coast through Ashford, Harrietsham, Maidstone, Riverhead/Sevenoaks, Oxted, Godstone, Redhill, Reigate, Dorking, Gomshall, Chilworth, Shalford and ending in Guildford.
Its composition is mainly Gault Clay and Upper Greensand, although the Lower Chalk area at the foot of the Downs is included in the area. The vale ascends and descends many times to allow for different headwaters to rise before they pass through the North Downs of its east-west flowing rivers, four times rising gently towards Lenham and Westerham (Kent), Reigate and Wotton (Surrey). Geologically it makes sense to study the whole as a unit.
The headwaters of the River Stour flows along the vale as does the River Medway for part of its length, further to the west, then do the River Darent, River Mole and River Tillingbourne.