Caulerpa obscura is a species of seaweed in the Caulerpaceae family.
The seaweed has a robust stolon with simple dark green fronds reaching 10to in height and 2to wide.
The species is found in rock pools and platforms in the upper sublittoral region up to a depth of 35m (115feet). 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.