Similar to a difference in elevation, potential energy is also associated with a difference in salt concentration so that electric power can eventually be produced by exploiting the salinity gradient between freshwater of rivers and seawater. Unfortunately, exploiting the salinity gradient for power production is not so easy as waterfalls. The potential energy implied in this salinity difference is of the same order of a hundred meter high water drop. The present technology advancement is still far from any commercial application. This chapter presents the different technologies, such as, The Pressure Retarded Osmosis (PRO) technology and The Reverse Electrodialysis (RED) Technology, for power generation from salinity gradient, which have been so far proposed in the technical literature pointing out the theoretical operating principles, the possible plant configurations and identifying the development gap to bridge so as to achieve technical and economical maturity.