Attaining an unconfirmed length of 3 m, the Mekong giant catfish grows extremely quickly, reaching a mass of 150 to 200 kg in only six years. The largest catch recorded in Thailand since record-keeping began in 1981 was a female measuring 2.7 m (roughly 9 feet) in length and weighing 293 kg (646 lb). This specimen, caught in 2005, is widely recognized as the largest freshwater fish ever caught (although sturgeon can far exceed this size, they can be anadromous). Mekong giant catfish have been confirmed as anadromous also. Thai Fisheries officials stripped the fish of its eggs as part of a breeding programme, intending then to release it, but the fish died in captivity and was sold as food to local villagers.
Grey to white in colour and lacking stripes, the Mekong giant catfish is distinguished by the near-total lack of barbels and the absence of teeth.