A new isomalabaricane-type triterpenoid, jaspiferin G (1), together with four known isomalabaricane-type triterpenoids, isogeoditin A (2), 13-(E)-isogeoditin A (3), jaspolide E (4), and 22,23-dihydrostellettin D (5), was isolated from the marine sponge Jaspis stellifera. The structures were elucidated on the basis of spectroscopic data ((1)H and (13)C NMR, (1)H(-1)H COSY, HSQC, HMBC, and ROESY) and mass spectrometry.