Cliona viridis, commonly called the green boring sponge, is a species of demosponge in the family Clionaidae.

In limestone and other calcareous substrates it excavates channels and chambers while on other types of rock it encrusts the surface or forms massive structures.

[2] The exterior appearance of this sponge in its later growth stages is a smooth mosaic-like surface composed of a firm, tough material.

[3] Cliona viridis is found in the East Atlantic, the Azores, the Cape Verde Islands, the Mediterranean Sea and the Indian Ocean.

[6] Cliona viridis is oviparous, that is to say the eggs are fertilised internally, sperm being drawn into the interior of the sponge with the incoming water flow.

There is some degree of synchronisation of the reproductive process as a larval bloom was observed to take place in June during a study undertaken in the Mediterranean.