Gloydius is a genus of pit vipers endemic to Asia, also known as Asian moccasins or Asian ground pit vipers. Named after American herpetologist Howard K. Gloyd, this genus is very similar to the North American genus Agkistrodon. 24 species are currently recognized.
Species of Gloydius are found in Russia, east of the Ural Mountains through Siberia, Iran, Himalayas from Pakistan, India, Nepal, China, Korea, Japan and the Ryukyu Islands.
(*) Not including the nominate subspecies.<br> <span style="font-size:100%;">(<sup>T</sup></span>) Type species.
In the above list, a taxon author in parentheses indicates that the species was originally described in a different genus.
Due to the strong morphological similarity, these snakes were classified in the genus Agkistrodon until very recently. However, by 1999 cladistic studies clearly showed that Agkistrodon did not form a clade (indeed, it was not even paraphyletic) and was thus split into several genera.
A new species, G. tsushimaensis, was described by Isogawa, Moriya & Mitsui (1994). It is referred to as the Tsushima island pitviper and is found only on Tsushima Island, Japan.