Besides wind and solar-based renewable energy technologies, marine sources are being actively discussed. Sources of marine renewable energy traditionally have included ocean currents, ocean waves, tides, thermal gradients, and salinity gradients. Salinity gradient power (SGP) is an attractive marine renewable resource because it possesses not only the largest energy potential but likely the largest total available resource as well. SGP is instantly available when diluted and concentrated ionic solutions are mixed; is renewable, sustainable, and produces no CO2 emissions or other significant effluents that may interfere with global climate. The ultimate challenge is in the economics of the recovery method used and the matching of the resulting energy density delivered to a suitable end application. The transformative technical challenges required in advancing the knowledge and understanding of SGP, both within and across related scientific fields, lies in advances in membrane development, supply source utilization, energy generation, and storage/delivery of the generated power. This article begins with an introductory overview of SGP, provides background into the major SGP membrane-based processes under development, and then discusses recent investigative results into the use of bipolar membranes in SGP generation applications.