Oleyl alcohol , or cis-9-octadecen-1-ol, is an unsaturated fatty alcohol with the molecular formula C₁₈H₃₆O or the condensed structural formula CH₃(CH₂)₇−CH=CH−(CH₂)₈OH. It is a colorless oil, mainly used in cosmetics.

It can be produced by the hydrogenation of oleic acid esters by Bouveault–Blanc reduction, which avoids reduction of the C=C group (as would occur with usual catalytic hydrogenation). The required oleate esters are obtained from beef fat, fish oil, and, in particular, olive oil (from which it gains its name). The original procedure was reported by Louis Bouveault in 1904 and subsequently refined.

It has uses as a nonionic surfactant, emulsifier, emollient and thickener in skin creams, lotions and many other cosmetic products including shampoos and hair conditioners. It has also been investigated as a carrier for delivering medications through the skin or mucus membranes; particularly the lungs.