Abstract: With the growing demand for green and sustainable materials, aqueous zinc-ion batteries (AZIBs) have shown great promise for large-scale energy storage due to their intrinsic safety, low cost, and high theoretical capacity. However, issues such as dendrite growth, hydrogen evolution reaction, and corrosion at the zinc anode severely limit their cycling stability and practical application. Among various strategies, developing high-performance biomass-based separators has emerged as an effective approach to stabilizing zinc anodes. This manuscript systematically reviews the research progress of functional separators based on cellulose, nanocellulose, cellulose derivatives, and other biomass materials in AZIBs. The preparation methods-including vacuum filtration, solution polymerization, surface engineering, dissolution-regeneration processes, and TEMPO-mediated oxidation-as well as structural characteristics such as pore size distribution, mechanical properties, thermal stability, and ion transport performance, are thoroughly analyzed. The review highlights the notable advantages of biomass-based separators in terms of mechanical strength, electrochemical performance, sustainability, and functional versatility. On this basis, future research directions toward high-performance and sustainable green energy storage devices are discussed, along with an assessment of the scalability of fabrication processes and their compatibility with existing battery production lines. This review aims to promote the industrial application of high-performance, low-cost biomass-derived separators.