Abstract <p>The fast demise of fossil fuels and increasing adverse environmental impacts resulting from their utilization has intensified the demand for renewable and sustainable energy sources. Hydrothermal liquefaction (HTL) has emerged as a promising thermochemical process for converting wet biomass into high quality bio-oil, offering a sustainable pathway for renewable energy production. This review provides a comprehensive analysis of diverse feedstocks utilized in HTL, highlighting their unique characteristics and implications on bio-oil yield and quality. The operating parameters, such as temperature, pressure, residence time, and biomass to solvent ratio, are discussed in detail, emphasizing their critical role in optimizing the process efficiency and product properties. It highlights the critical role of catalysts, such as metal-based and zeolite catalysts, in enhancing biomass transformation through reactions like deoxygenation, hydrogenation, and cracking. Additionally, this review explores various reactor configurations and novel designs, outlining their distinct advantages based on feedstock properties and operational requirements. Strategies for upgrading and synthesizing advanced bio-oil, such as fast HTL, hydrotreating and co-processing, are discussed as essential steps toward producing drop-in fuels compatible with existing energy infrastructure. This review underscores the advancements and future potential of HTL technology as a cornerstone for sustainable biofuel production and a circular bioeconomy.</p> Highlights <p>• HTL diverse feedstocks and operating parameters for producing bio-oil are discussed</p> <p>• Emphasized the influence of catalysts on biomass transformation</p> <p>• Various reactor types provide unique advantages based on feedstock and operation</p> <p>• The quality of HTL bio-oil and future synthesis/upgrading</p> Graphical Abstract <p></p>