Chemical investigation of a marine sponge, Euryspongia sp., collected from the Great Australian Bight, Australia, resulted in the isolation of two new sesquiterpene quinones , deoxyspongiaquinone (4) and (E)-chlorodeoxyspongiaquinone (5), as well as two sesquiterpene hydroquinones, deoxyspongiaquinol (6) and (E)-chlorodeoxyspongiaquinol (7). The structures for (4)-(7) were determined by detailed spectroscopic analysis, as well as chemical interconversion and degradation.