The absolute configuration of the pentacyclic ichthyotoxin stypotriol, a constituent of Stypopodium zonale, was deduced to be 3S,5R,8R,9R,10S,13S,14S-(-)-1 by vibrational circular dichroism spectroscopy of the derived triacetate 2 in comparison to DFT B3LYP/DGDZVP calculations. Compound 2, C33H46O7 having 300 electrons, is the largest natural product successfully studied by VCD to date.