Hydon's Ball is a 587 foot hill on Hydon Heath, Surrey, England. It is situated roughly 6 km (3.5 miles) south east of Godalming, in central southern England. It is adjacent to the hamlet of Hydestile, near the village of Hambledon.
Sometimes known as Hydon Ball, or Cup Hill, it is now in the care of the National Trust. At its highest point is a large stone seat which was placed there in 1915 as a memorial to Octavia Hill, one of the Trust's founders.
It is believed that the term "ball" refers to a signalling station which once stood at the top of the hill. (Typically, "ball" signalling stations were used to synchronize the time visually at given points during the day across long distances.)