The global imperative to transition from fossil-dependent industries toward sustainable, circular production models has positioned lignocellulosic biomass as a cornerstone feedstock for the modern bioeconomy. This chapter provides a critical synthesis of lignocellulosic biorefineries, evaluating the integrated processes and diverse value chains required to transform complex plant matter into high-value commodities. While the tripartite structure of cellulose, hemicellulose, and lignin offers immense potential for the production of biofuels, bioenergy, and platform chemicals, its inherent recalcitrance poses a formidable barrier to commercial viability. To address this, the chapter systematically examines various pretreatment approaches, including physical, chemical, physicochemical, and biological methods, highlighting their mechanisms, advantages, and limitations. Emerging green and sustainable technologies, such as deep eutectic solvents, ionic liquids, and supercritical fluid-based processes, are also critically discussed in the context of improving biomass fractionation and process sustainability. Subsequently, key conversion pathways such as thermal, thermochemical, and biochemical are explored for the valorization of lignocellulosic biomass into fuels, platform chemicals, and other value-added products. It highlights recent breakthroughs in enzymatic saccharification and microbial fermentation, with a focus on how metabolic engineering and process optimization are currently overcoming traditional yield limitations. The chapter further addresses integrated and hybrid biorefinery concepts, such as consolidated bioprocessing and process intensification, which aim to maximize resource utilization and economic feasibility. Overall, this chapter provides critical insights into current advancements, challenges, and future prospects of lignocellulosic biorefineries in advancing a sustainable and carbon-neutral bioeconomy.