Achiral phase-transfer catalysts (PTCs) are quaternary ammonium or phosphonium salts that facilitate the migration of anions from one phase (typically aqueous) into another (typically organic) where the reaction takes place. These catalysts enhance the reactivity of ionic species by solubilizing them in organic solvents, often allowing for reactions under biphasic or even solvent-free conditions. Common achiral PTCs include tetrabutylammonium bromide (TBAB), tetrabutylammonium hydrogen sulfate (TBAHS), and Aliquat 336. PTCs are essential in a wide range of reactions such as nucleophilic substitutions, oxidations, alkylations, and Wittig reactions. While achiral by design, these catalysts are vital in process chemistry, particularly for scale-up, because they can improve yields, reduce side reactions, and allow milder reaction conditions. In green chemistry, their role is further emphasized due to their ability to minimize solvent use and enable environmentally benign reaction pathways. Though lacking enantioselectivity, achiral PTCs remain indispensable tools in both academic and industrial synthetic strategies.