Four new sesterterpenes, namely, (+)-20-formylhyrtiosal (1), (+)-16-O-acetyl-20-formylhyrtiosal (2), 12-alpha-O-acetylhyrtiolide (3), and 5,10-dihydroxyfurospinulosine-1 (4), together with seven known sesterterpenes (5-11) were isolated from the marine sponge Hyrtios erectus collected at Hainan, China. The structures were elucidated on the basis of extensive spectroscopic analysis involving mainly one- and two-dimensional NMR as well as mass spectroscopy.