The Kehelgamu Oya (translated into Kehelgamu River from Sinhala) is a major upstream tributary of the Kelani River in Sri Lanka. The tributary measures in length, originating in the hills of the Horton Plains National Park, before passing through the Castlereigh Reservoir. Kehelgamu Oya converges with the Maskeliya Oya at Kalugala, forming the long Kelani River. The river is heavily used for hydroelectric power generation.
The following table lists the features along the Kehelgamu Oya, from its origins further upstream. Some dams hold back water, and transfer a percentage of it to hydroelectric power stations located further downstream, via tunnels.