Hydrothermal liquefaction (HTL)Hydrothermal Liquefaction (HTL) enables the conversion of wet biomassWet biomass into biocrudeBiocrude by applying high temperatures and pressures, effectively removing the necessity for energy-intensive drying steps. This chapter evaluates HTL’s ability to produce biofuelsBiofuel like syngasSyngas, biocrudeBiocrude, and biocharBiochar from various feedstocks, including food wasteWastes, sewage sludge (SS), and algae. The impactsImpact on yield and quality of three key process variables are examined: residence time, temperature (250–400°C), and catalysts (such as alkali metals). Recent innovations, including continuous-flow reactors and catalytic HTL, are discussed along with problems like reactor corrosion and nutrient recovery. While there are financial obstacles, such as high capital costs, there are also environmental advantages, such as lower carbon footprintsFootprints than with pyrolysisPyrolysis. New applications in wastewater treatment and aviation fuel production demonstrate HTL’s versatility. Research shows that HTL holds significant promise as an alternative method for processing high-moisture biomass within the energy sector. Besides the biocrude yield, operating conditions also influence the initial selection of both biomass feedstockBiomass feedstock and catalysts. When conditions are satisfied, co-processing biocrudeBiocrude alongside conventional crude oil allows for using existing refinery infrastructure, thereby circumventing the need for significant capital investment in new biorefineryBiorefinery facilities. The chapter discusses future prospects, including integrating HTL with carbon capture technologies and applying AI-driven process optimizationProcess optimization.