Caulerpa obscura is a species of seaweed in the Caulerpaceae family.

[1] The seaweed has a robust stolon with simple dark green fronds reaching 10 to 30 centimetres (3.9 to 11.8 in) in height and 2 to 6 cm (0.79 to 2.36 in) wide.

[1] The species is found in rock pools and platforms in the upper sublittoral region up to a depth of 35 metres (115 ft).

In Western Australia, it is found along the coast in the Mid West and south as far as Esperance[1] it is also found in South Australia, Victoria and Tasmania.