<p>Lignocellulosic biomass (LCB), the most abundant renewable resource on Earth, poses severe environmental challenges when improperly disposed of as waste. Current utilization approaches for these waste materials are generally low in added value, making it essential to develop efficient valorization pathways. Nanocellulose production from LCB is particularly attractive because it converts low-cost and cellulose-rich residues into high-value nanomaterials with excellent mechanical strength, high specific surface area, biodegradability, and tunable surface chemistry, thereby reducing dependence on fossil-based polymers and expensive purified cellulose sources. This review summarizes recent advances in nanocellulose production from LCB, with emphasis on feedstock characteristics, cellulose structural foundations, pretreatment strategies, mechanical and chemical isolation methods, green solvent systems, and biological routes. The efficiency, energy consumption, environmental impact, scalability, and product performance of different extraction pathways are systematically compared. Despite significant progress, several critical gaps remain, including high chemical and energy consumption during scale-up, insufficient solvent and reagent recovery, the lack of standardized eco-friendly extraction protocols, and limited understanding of how extraction conditions determine nanocellulose morphology, surface chemistry, and application-specific performance. Moreover, the translation of LCB-derived nanocellulose into high-value applications is still constrained by inconsistent product quality, weak techno-economic validation, and insufficient life-cycle assessment. This review therefore provides a comprehensive technical summary and forward-looking perspective, aiming to clarify the relationships among biomass structure, extraction strategy, nanocellulose properties, and practical applications, and to support the sustainable development of the nanocellulose industry.</p> Graphical Abstract <p></p>