The Sri Lanka cat snake, Boiga ceylonensis, is a species of colubrid snake found in Sri Lanka and the Western Ghats of India.
The species can be identified from other members of the genus Boiga by the following scalation and taxonomic characters. The anterior palatine and mandibular teeth are not any larger than those at the posterior positions. The eye is shorter than the snout. The rostral scale is broader than deep, the internasals are shorter than the prefrontals. The frontal scale is longer than its distance from the end of the snout and a little shorter than the parietals. The loreal is square and deeper than long, one or two preoculars reach the upper surface of the head. There are two postoculars, the temporals are small 2+3 or 3+3. There are 8 upper labials with the third, fourth and fifth touching the eye. There are 4 lower labials in contact with the anterior chin-shields and are shorter than the posterior. Scales in 19 or 21 rows, not very oblique ; scales along the vertebral row much enlarged, and at mid body nearly as broad as long. Ventrals scutes 214-249 ; the anals are undivided, subcaudals 90-117.
The colour is brown or greyish above, with a series of blackish transverse spots or bands ; nape with a blackish blotch, or three blackish longitudinal streaks, or a transverse bar ; a more or less distinct brown streak from the eye to the angle of the mouth ; lower parts yellowish, dotted with brown, usually with a lateral series of brown spots. They are about 4 feet long from tip to tip with the tail 10 inches. They are found in the Western Ghats and Sri Lanka.