A key challenge in industrial processes is replacing fossil-based solvents with sustainable, renewable alternatives while minimizing industrial waste and enhancing sustainability. Deep eutectic solvents (DESs), with their exceptional properties, offer a promising solution. These solvents can be tailored from a wide variety of hydrogen bond donors (HBDs) and acceptors (HBAs), making them highly customizable, cost-effective, and versatile. Moreover, their excellent biocompatibility and biodegradability position them as ideal candidates for green chemistry applications. DESs are easy to prepare and offer numerous advantages, often serving a dual role as both solvents and active catalysts, depending on their composition and molar ratios. One particularly interesting HBD component for DESs is -toluenesulfonic acid (PTSA)-a solid, stable, and affordable strong organic acid. PTSA interacts effectively with various HBAs, making it highly valuable for applications requiring strong acidity and proton availability. This review explores PTSA's diverse applications and highlights its untapped potential in DES formulations. Additionally, it provides insights into HBA selection tendencies based on specific applications and starting materials. By showcasing PTSA's advantageous properties and versatility, this review underscores its role in advancing green chemistry and fostering innovation in sustainable solvent development.