Pretreatment is the crucial step in the biorefinery process for the bioconversion of lignocellulosic biomass to value-added products. Among various chemical pretreatment methods, deep eutectic solvents (DESs) are novel green solvents to effectively reduce the recalcitrant nature of the biomass that result in an increase in the sugar and product yields after the enzymatic saccharification and fermentation process. This review summarizes the properties, mechanisms, applications and parameters of various types of DESs to improve the delignification from the lignocellulosic biomass and fractionation process. In addition, different integrated methods related to DES pretreatment used in recent studies are also discussed in this paper. Even though this strategy is in the infant stage, further research is required to meet the challenges and increase the efficiency of the process. Moreover, such an approach is desirable to ensure the extensive utilization of biomass for developing sustainable products by mitigating global energy crises. © 2023 Elsevier Ltd