Octadecyltrichlorosilane (ODTS or n-octadecyltrichlorosilane) is an organosilicon compound with the formula . A colorless liquid, it is used as a silanization agent to prepare hydrophobic stationary phase, for reversed-phase chromatography.
It is also evaluated for forming self-assembled monolayers on silicon dioxide substrates. Its structural chemical formula is CH<sub>3</sub>(CH<sub>2</sub>)<sub>17</sub>SiCl<sub>3</sub>. It is flammable and hydrolyzes readily with release of hydrogen chloride.
Dodecyltrichlorosilane, an ODTS analog with shorter alkyl chain, is used for the same purpose.
ODTS-PVP films are used in organic-substrate LCD displays.