Hydropower plants in the Franco-German Rhine region have been working on cross-border cooperation in the development of RES for electricity generation for a long time. Hydropower, that is, the production of electricity from moving water, is considered the most important and widely used renewable source of energy in this geographical area. Several hydropower plants for generating electricity have been built and operate in accordance with the international agreements and the respective regulations of the bordering countries. In addition to this strategic geographical location, hydropower plays an eminent role in the energy mix, which has an impact on the security of energy supply. Thus, there are significant national interests in the sector. In light of the historical commitment to hydropower and of the national strategic policies implemented in the sector, this contribution focuses on the Upper Rhine Region to demonstrate how the legal framework relating to hydropower has shaped Franco-German cross-border cooperation. By taking stock of this theoretical background, the present chapter analyses existing forms of cross-border cooperation on hydropower generation to consider future prospects in this field.