Dictyosphaeria cavernosa is a species of green algae (class Ulvophyceae) in the family Siphonocladaceae, one of the three species in this family. Its common name is green bubble seaweed.

Dictyospharea cavernosa is multicellular with multiple bumps or bubbles on the surface. Dictyosphaeria cavernosa is hollow in contrast to its sister species D. versluysii of the same appearance which is solid. It grows about 12cm in diameter and possesses a green-yellow color while young.