The Giant Tube Worm (Riftia pachyptila) is a marine invertebrate in the phylum Annelida (formerly grouped in phylum Pogonophora and Vestimentifera) related to tube worms commonly found in the intertidal and pelagic zones. Giant tube worms live on the floor of the Pacific Ocean near black smokers, and can tolerate extremely high hydrogen sulfide levels. These worms can reach a length of 3 m (9 ft 10 in), and their tubular bodies have a diameter of 4 cm (1.6 in). Ambient temperature in their natural environment ranges from 2 to 30 degrees Celsius.
The common name "giant tube worm" is however also applied to the largest living species of shipworm, Kuphus polythalamia, which despite the name "worm" is a bivalve mollusk, rather than an annelid.