Quaternium-15 (systematic name: hexamethylenetetramine chloroallyl chloride) is a quaternary ammonium salt that has been used as a surfactant and preservative.

It acts as an antimicrobial agent because it slowly releases formaldehyde, which is a preservative with biocidal properties.

[citation needed] The isolated cis-compound is used primarily in cosmetic applications, with a maximum permitted concentration in the EU of 0.2%.

The mixed product (cis- and trans-) is used in a wider range of formulations such as: emulsifiable metal-cutting fluids, latex and emulsion paints, liquid floor polishes and floor waxes, and glues and adhesives.

At low pHs, it would be expected to release significant amounts of formaldehyde due to acid hydrolysis via the Delepine reaction.