The EtOAc extract of a Taiwanese soft coral, Caldiella australis, yielded four new eunicellin-based diterpenoids, australins A-D (1-4). The chemical structures of these metabolites were determined on the basis of extensive spectroscopic (including 1D and 2D NMR) analyses and by comparison of their NMR spectral data with those of related metabolites. Metabolite 2 was found to possess a moderate cytotoxic activity against selected breast and liver cancer cell lines.