Ionic liquids (ILs) have attracted many researchers to work on them as an important ingredient in many applications. The chapter concerns the broad uses of ILs in pharmaceutical and diagnostics, extraction technologies, and waste management. They are flexible solvents and catalysts that promote green chemistry and aid in the efficient production of active pharmaceutical ingredients (APIs) in fine chemical and pharmaceutical sectors. In drug delivery, ILs enhance drug-protein binding affinity, enhance the permeability of medicines through biological membranes, and significantly enhance the solubility and bioavailability of poorly water-soluble substances. In medical applications, ILs are aiding the development of high-performance biosensors and electrochemical devices through improvements in sensitivity, signal stability, and biocompatibility. The latter is important with regard to the green extraction of bioactive compounds using microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and solid–liquid extraction (SLE). Also, they are good antistatic agents in polymers and are used to remove pollutants in wastewater, which contributes to sustainability.