Lumisterol is a compound that is part of the vitamin D family of steroid compounds. It is the (9ò,10ñ) stereoisomer of ergosterol and was produced as a photochemical by-product in the preparation of vitamin D<sub>1</sub>, which was a mixture of vitamin D<sub>2</sub> and lumisterol. Vitamin D<sub>2</sub> can be formed from lumisterol by an electrocyclic ring opening and subsequent sigmatropic [1,7] hydride shift.
Lumisterol has an analog based on 7-dehydrocholesterol, known as lumisterol 3.