Eleven new xenia diterpenoids, umbellacins A-G (1-7), 14,15-epoxy-xeniolide H (8), 3-acetyl-14,15-epoxy-xeniolide H (9), and umbellacins H and I (10, 11), were isolated from a methylene chloride-soluble fraction of the soft coral Xenia umbellata. The structures were elucidated by extensive spectroscopic analysis, and their cytotoxicity against selected cancer cells was measured in vitro.