Found in Asia in Nepal and Seven Sisters (Assam), India, eastward through Myanmar, Cambodia, Thailand, Laos, Vietnam, West Malaysia, Taiwan, Okinawa, Sumatra and Borneo.[1]
Species placed in this group have long been associated with the genus Trimeresurus.[1] One other species that is included in some other taxonomies is O. tonkinensis (Bourret, 1934). It is commonly called the Tonkin pit viper and is found in Vietnam and China.