Abstract : Owariensisone B-D, three new lactone iridoids, identified as lactone of α-(3-acetoxymethyl-2-hydromethylcyclopent-3-en-yl) ethanoic acid (1), lactone of α-(4-β-acetoxy-3-β-acetoxymethyl-2-hydromethyl-3-hydroxycyclopentyl) ethanoic acid (2) and lactone of α-(4-β-acetoxy-3-α-acetoxymethyl-2-hydromethyl-3-hydroxycyclopentyl) ethanoic acid (3) were isolated from the n-hexane extract of the whole plant of Brillantaisia owariensis. Their structures were established by interpretation of their spectral data, mainly ESI-HRMS(TOF), 1D-NMR (1H, 13C) and 2D-NMR (1H-1H COSY, HSQC, HMBC and ROESY) and by comparison with the literature data.