This chapter attempts to summarize the progress achieved in the development of reverse osmosis (RO) membranes, membrane fabrication procedures, and RO membrane applications. The chapter discusses the early stages of cellulose acetate membrane production, followed by thin film composite membranes and the most recent advancements in RO membrane fabrication using nanocomposite and biomimetic membranes. This chapter also discusses the applications of RO membranes in desalination and wastewater treatment, and other industrial applications. Finally, the chapter discusses the future of RO membrane processes.