Deep eutectic solvents (DESs) are a class of sustainable and flexible solvents characterized by hydrogen bonding interactions between hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs), which significantly reduce their melting points. Due to their considerably reduced volatility, ease of preparation, and compatibility with green chemistry principles, DESs have emerged as alternative solvents to traditional organic solvents and ionic liquids (ILs) for various applications. The flexible composition of DESs enables the design of their properties to fit a wide variety of applications, ranging from catalytic and electrochemical reactions to bioprocessing and extraction methods. Furthermore, biocompatibility features have expanded the use of natural deep eutectic solvents (NADESs) in the life sciences. However, they are hampered by some limitations, such as higher viscosity, moisture sensitivity, and insufficient toxicological data, which limit their use to industrial-scale processing at large scales. Ongoing efforts are aimed at improving the understanding of the structure-activity relationship and developing predictive models that enable the rational design of DESs. As novel solvents, DESs have immense potential to transform green chemical processes in both industrial and research environments.