A novel norditerpenoid, sinuleptolide [(1S,5S,8S,10R,11S)-11-hydroxy-1-isopropenyl-8-methyl-3,6-dioxo-5,8-epoxycyclotetradec-12-ene-10,12-carbolactone] [1], was isolated from the Okinawan soft coral Sinularia sp. The structure of 1 was established mainly on the basis of nmr spectroscopic data.