The increasing occurrence of oil spills and oily wastewater discharges poses severe environmental and economic challenges, highlighting the urgent need for efficient and sustainable separation technologies. In recent years, three-dimensional (3D) porous polysaccharide-based materials have emerged as eco-friendly and versatile candidates for oil/water separation. Derived from natural polymers such as cellulose, chitosan, alginate, and starch, these materials combine biodegradability, biocompatibility, and functional tunability with unique structural advantages, including high porosity, large surface area, and adjustable wettability. This chapter provides a comprehensive overview of superwetting 3D polysaccharide materials, sponges, aerogels, hydrogels, and 3D-printed scaffolds, engineered for efficient separation of stratified and emulsified oil/water mixtures. The discussion highlights fabrication methods such as freeze-drying, supercritical drying, chemical modification, and additive manufacturing, emphasizing how these strategies enhance wettability, mechanical stability, recyclability, and anti-fouling properties. Examples demonstrate separation efficiencies exceeding 98%, high oil absorption capacities, and strong reusability across diverse environmental conditions. Notably, the chapter underscores the sustainability benefits of polysaccharide-based systems, including the valorization of biomass and waste feedstocks into high-value functional materials. Finally, current limitations, such as scale-up challenges, long-term durability, and the trade-off between mechanical strength and porosity, are critically assessed. Future research opportunities lie in multifunctional composites, bio-inspired designs, and advanced 3D printing techniques, paving the way toward greener, cost-effective, and durable separation platforms for environmental remediation.