The widest freshwater fish and the largest stingray in the world, this species grows up to 2.2 m (7.2 ft) across and can exceed 300 kg (660 lb) in weight.

This species is uniformly grayish brown above and white below; the underside of the pectoral and pelvic fins bear distinctive wide, dark bands on their posterior margins.

Females give live birth to litters of one to four pups, which are sustained to term by maternally produced histotroph ("uterine milk").

This species faces heavy fishing pressure for meat, recreation, and aquarium display, as well as extensive habitat degradation and fragmentation.

Bleeker named the new species polylepis, from the Greek poly ("many") and lepis ("scales"), and assigned it to the genus Trygon (now a synonym of Dasyatis).

[2][3] However, in subsequent years Bleeker's description was largely overlooked, and in 1990 the giant freshwater stingray was described again by Supap Monkolprasit and Tyson Roberts in an issue of the Japanese Journal of Ichthyology.

[4] On the other hand, comparison of freshwater whipray DNA and amino acid sequences between India and Thailand has revealed significant differences.

[7] Finally, additional research is needed to assess the degree of divergence amongst populations of U. polylepis inhabiting various drainage basins across its distribution, so as to determine whether further taxonomic differentiation is warranted.

[12] Disjunct populations of the giant freshwater stingray in separate river drainages are probably isolated from one another; though the species occurs in brackish environments, there is no evidence that it crosses marine waters.

[9] The diet of the giant freshwater stingray consists of small, benthic fishes and invertebrates such as crustaceans and molluscs, which it can detect using its electroreceptive ampullae of Lorenzini.

[1][13] Parasites documented from this species include the tapeworms Acanthobothrium asnihae, A. etini, A. masnihae, A. saliki, A. zainali,[14] Rhinebothrium abaiensis, R. kinabatanganensis, and R.

[15] The giant freshwater stingray is viviparous, with the developing embryos nourished initially by yolk and later by histotroph ("uterine milk") provided by the mother.

[10][16] It is reputedly difficult and time-consuming to catch; a hooked ray may bury itself under large quantities of mud, becoming almost impossible to lift, or drag boats over substantial distances or underwater.

[16] In the Mae Klong and Bang Pakong Rivers, the giant freshwater stingray is also increasingly targeted by sport fishers and for display in public aquariums.

[1] The major threats to the giant freshwater stingray are overfishing and habitat degradation resulting from deforestation, land development, and damming.

[1][17] In the 1990s, the Thai government initiated a captive breeding program at Chai Nat to bolster the population of this and other freshwater stingray species until the issue of habitat degradation can be remedied.