Surrey is a county in South East England which borders Kent to the east, East Sussex to the southeast, West Sussex to the south, Hampshire to the west, Berkshire to the northwest, and Greater London to the northeast. With about 1.2 million people, Surrey is the 12th-most populous English county, the third-most populous home county, after Kent and Essex, and the third-most populous in the Southeast, after Hampshire and Kent.

Surrey is divided in two by the chalk ridge of the North Downs, running east–west. The ridge is pierced by the rivers Wey and Mole, tributaries of the Thames, which formed the northern border of the county before modern redrawing of county boundaries, which has left part of its north bank within the county. To the north of the Downs the land is mostly flat, forming part of the basin of the Thames. The geology of this area is dominated by London Clay in the east, Bagshot Sands in the west and alluvial deposits along the rivers.

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