<p>With the acceleration of global industrialization and urbanization, environmental issues such as oil spills and industrial wastewater pollution are intensifying, posing severe threats to aquatic ecosystems and human health. Cellulose-based aerogels, with their unique three-dimensional nanoporous structure and tunable surface chemistry, have become a promising material for oil–water separation due to their excellent selective adsorption, recyclability, environmental compatibility, and cost-effectiveness. This review systematically discusses the critical value of cellulose-based aerogels in oil–water separation, elaborates on the technical characteristics of their fabrication processes and drying methods, and provides an in-depth analysis of their technical advantages and development prospects in practical applications, including emergency oil spill treatment, oil–water emulsions separation, advanced purification of industrial oily wastewater, and separation in complex environmental media.</p>