This work analyzes five major bilateral treaty regimes on the South Asian subcontinent: between India and Bangladesh for the Ganges River; India and Nepal for the Kosi, Gandaki, and Mahakali rivers; and India and Pakistan for the Indus River. It also explains the legal regimes of these rivers in the context of the serious challenges to the water resources of the subcontinent posed by significant population increases, urbanization, industrialization, and environmental degradation.