Holothuria atra, commonly known as the black sea cucumber or lollyfish, is a species of marine invertebrate in the family Holothuriidae.

[3][4] Holothuria atra is found in the tropical Indo-Pacific region, its range extending from the Red Sea and East Africa to Australia.

It is found on the seabed, in shallow waters on reefs and sand flats and in seagrass meadows at depths of up to 20 metres (66 ft).

[5] Holothuria atra, like many echinoderms, engage in sediment bioturbation—a process which plays an important role in the health of coral reefs.

[4] On Guam, the toxic red fluid that Holothuria atra releases is utilized to drive octopuses out of hiding holes.

[11] Compounds of potential biomedical importance are present in Holothuria atra, including lectin, steroidal sapogenins and triterpene glycoside.