The titan triggerfish, giant triggerfish or moustache triggerfish (Balistoides viridescens) is a large species of triggerfish found in lagoons and at reefs to depths of in most of the Indo-Pacific, though it is absent from Hawaii. With a length of up to , it is the largest species of triggerfish in its range (the stone triggerfish, Pseudobalistes naufragium, from the east Pacific is larger).
Behavior
thumb|With [[orange-lined triggerfish and moorish idols, in the Maldives.|left]]
The titan triggerfish is diurnal and solitary. It feeds on sea urchins, molluscs, crustaceans, tube worms and coral.
Titan triggerfish have been observed being aggressive to other fish who enter their territory.
Interaction with humans
thumb|Speared in [[French Polynesia]]
Though titan triggerfish are usually wary of divers and snorkelers, females can be territorial and aggressive around their nests during the reproduction season, which occurs for about a week in each month (either after the full moon or new moon, depending on the population).
The nest is placed in a flat sandy area, and is defended vigorously against any intruders. The territory around the nest is roughly cone-shaped and divers who accidentally enter it may be attacked. Divers should swim horizontally away from the nest rather than upwards which would only take them further into the territory. Although bites are not venomous<!--beware: One webpage mistakenly confused its non-venomous bite and its sometimes ciguatoxic flesh-->, the strong teeth can inflict serious injury that may require medical attention.
The threat posture includes the triggerfish facing the intruder while holding its first dorsal spine erect.