Cliona celata, occasionally called the boring sponge, is a species of demosponge belonging the family Clionaidae. It is found worldwide. This sponge creates round holes up to 5 millimetres (0.20 in) in diameter in limestone or the shells of molluscs, especially oysters. The sponge itself is often visible as a rather featureless yellow or orange lump at the bottom of the hole.