This chapter is a depiction and overview of the basic information of the physicochemical properties of deep eutectic solvents (DESs), which are environmentally benign solvents. These solvents have created inquisitiveness in the scientific community and are emerging as an attractive replacement to ionic liquids (ILs), have greener accreditation than ILs, and are propitious for various industrial applications. DESs usually have a composition of hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) in a distinct molar ratio via hydrogen bonds. Specific physicochemical properties possessed by a credible DES include ionic conductivity, viscosity, refractive index, freezing temperature, density, and surface tension. Apart from the molar ratios of HBA and HBD, factors like water content, temperature, and synthesis methods also have a substantial influence on their physicochemical properties. In every area of study, it is crucial to properly collect a basic physicochemical characteristic of the material. Since some researchers have measured esoteric properties that are highly relevant for particular applications, such as changes in molar volume, changes in thermal stability, activity coefficients, molar heat capacity, polarity measurements, enthalpies of mixing, and many more, the list of properties that are important for DESs is by no means exhaustive. The main physicochemical characteristics of DESs that are relevant to the greatest number of fields, however, will be discussed in this chapter. To gain a comprehensive understanding of DESs and to advance efforts toward building a robust theoretical and practical framework, an in-depth analysis of these properties is indispensable. This section will present the key physicochemical parameters of DESs and outline the experimental techniques commonly employed in their characterization.