The novel 9,11-secosteroid, haebaruol, was isolated from the soft coral Clavularia sp. collected from the Ishigaki Island, Okinawa, Japan. The planar structure of haebaruol was elucidated by NMR spectroscopic analysis and its relative and absolute stereochemistry was determined by X-ray crystallographic analysis and a modified Mosher's method. Haebaruol exhibited cytotoxicity against HeLa cells.