This volume includes selected contributions presented during the 3rd edition of the international conference on WaterEnergyNEXUS, which was held in Tunisia in December 2020.  This conference was organized by the University of Sfax (Tunisia), in cooperation with the Sanitary Environmental Engineering Division (SEED) of the University of Salerno (Italy), the Advanced Institute of Water Industry at Kyungpook National University (Korea) and The Energy and Resources Institute, TERI (India). The WaterEnergyNEXUS series of conferences are supported by the UNESCO World Water Association Programme...