Deep eutectic solvents (DESs) are a new class of green chemistry solvents that provide a sustainable, eco-friendly alternative to conventional organic solvents and ionic liquids. DESs have low toxicity, are biodegradable, cost-effective, and highly customisable, making them perfect for a wide range of applications. DESs are formed by combining hydrogen bond donors (HBDs) and acceptors (HBAs) having melting points lower than their individual components, which makes them suitable for use in fields like biomass processing, CO2 capture, pharmaceuticals, energy storage, and nanotechnology. This chapter focuses on the latest developments in DES synthesis, focusing on green methods and cutting-edge computational tools like COSMO-RS and MD simulations for modifying their properties. Role of DESs in green chemistry spans a wide range of applications, from the valorisation of lignocellulosic biomass and CO2 adsorption to advancements in drug delivery systems. Furthermore, modern characterisation techniques such as NMR and FTIR spectroscopy, along with emerging machine-learning approaches, are increasingly being employed to analyse, predict, and optimise DES properties, thereby paving the way for smarter, more efficient, and environmentally sustainable solutions.