Caulerpa obscura is a species of seaweed in the Caulerpaceae family.
The seaweed has a robust stolon with simple dark green fronds reaching in height and wide.
The species is found in rock pools and platforms in the upper sublittoral region up to a depth of . In Western Australia, it is found along the coast in the Mid West and south as far as Esperance it is also found in South Australia, Victoria and Tasmania.