Trimeresurus insularis or Indonesian pit viper, Lesser Sunda Islands pit viper, Sunda white-lipped pit viper, red-tailed pit viper is a venomous pit viper species found in eastern Java and the Lesser Sunda Islands, Indonesia.

[4] Their color patterns are often found to be green or a blue-green color with specific populations even containing yellow variants as well.

[5] It is found in Indonesia on eastern Java, Adonara, Alor, Bali, Flores, Komodo, Lombok, Padar, Rinca, Romang, Roti, Sumba, Sumbawa, Timor, and Wetar and East Timor.

[1][3] The type locality given is "Soe, Timor".

[2][3] They are arboreal[3][6] and can be found in dry monsoon forests at elevations up to 1,200 m (3,900 ft) above sea level.