Waste biomass feedstocks, including food waste, animal manure, forestry residues, and sewage sludge, can be utilized to produce a valuable oily substance known as biocrude oil. Biocrude oil production involves biomass hydrothermal liquefaction (HTL). HTL offers key advantages, such as using water as a catalyst, recirculating and recycling water generated during the process, and eliminating the need to dry the biomass before conversion. These factors contribute to reducing production costs through the HTL process, making it an appealing method within a biorefinery framework. This chapter highlights several recent applications of biocrude oil production from waste biomass feedstocks. Results from pilot-scale plants and techno-economic analyses indicate a promising future for the HTL process. However, using waste biomass as a feedstock presents challenges due to high pretreatment costs, posing an obstacle to the widespread application of HTL on a full scale.