The Gudgenby River is a river in the Australian Capital Territory that flows predominantly through the forests of the Namadgi National Park. The river catchment contains ecologically significant alpine wetlands. It flows into the Murrumbidgee River immediately upstream of Tharwa village and to the south of Canberra.
The Gudgenby has been investigated as a site for a new dam to provide water to the ACT. Two dams have been proposed for construction near Mount Tennent, a small dam with a capacity of approximately 43 GL or a large 159 GL capacity dam which would more than double water storage capacity in the ACT.