Tetraoctylammonium iodide is an organic compound classified as a quaternary ammonium salt. It is commonly used as a phase-transfer catalyst, facilitating reactions between two immiscible phases, such as aqueous and organic phases. Tetraoctylammonium iodide has various applications in organic synthesis, particularly in reactions involving nucleophilic substitution, oxidation, and reduction. Additionally, it serves as a surfactant and emulsifier in both industrial and laboratory settings.