The title compound, C10H18, a decalin stereoisomer, crystallizes with Z' = 0.5 in the space group P21/n. The trans-decalin molecule is located on an inversion centre with both rings in a chair conformation, making for a quasi-flat overall shape. Despite the absence of hydrogen bonds, it crystallizes easily. In this work the unknown crystal structure of trans-decalin has been solved and refined using X-ray powder diffraction data.