The River Whitewater is a spring-fed stream rising near Bidden Grange Farm, between Upton Grey and Greywell in Hampshire, England. From its source, the river flows northeast before joining the River Blackwater near Swallowfield, passing through the settlements of Greywell, North Warnborough, Hook, Hartley Wintney, Rotherwick, West Green, Mattingley, Bramshill, and Heckfield along the way. As a spring-fed system, the upper reaches tend to carry clearer, more stable water, while the lower reaches take on more colour and exhibit a somewhat less stable flow regime with slightly steeper banks. The river is a classic southern English mixed fishery, holding both game and coarse species, and several sections are managed as dedicated trout fisheries where wild fish are supplemented with hatchery stock.