The fugu in Japanese, bogeo or bok (복) in Korean, and hétún in Standard Modern Chinese is a pufferfish, normally of the genus Takifugu, Lagocephalus, or Sphoeroides, or a porcupinefish of the genus Diodon, or a dish prepared from these fish.

Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish, it is found in several other animals. It is also produced by certain infectious or symbiotic bacteria like Pseudoalteromonas, Pseudomonas, and Vibrio as well as other species found in symbiotic relationships with animals and plants.