Cationic surfactants are being used in various applications industrially and domestically for a long time. Pyridinium salts come under the category of cationic surfactants. These are unsaturated heterocyclic compounds having different functional groups present either on pyridine ring or at nitrogen atom. Initially, they were only considered as effective germicides. Several researches have been done for the modification of the properties of these salts, making them important for various applications. This paper reviews the types, synthesis, properties, and applications of quaternary pyridinium salts.