We describe a new species of Calamaria Boie on the basis of a single specimen collected in broadleaved evergreen forest from Gia Lai Province, Central Vietnam. This is a large species (total length of the unique male 457 mm) characterized by rostral wider than high, with portion visible from above more than half of prefrontal suture; paraparietal surrounded by five shields and scales; presence of preocular; four supralabials, of which second and third entering orbit; modified maxillary teeth; five infralabials, of which first three are in contact with anterior chin shield; mental touching anterior chin shields; 3 191 ventrals, single anal scale; 23 divided subcaudal scales; tail relatively short, as thick as body, not tapering, with rounded end (8.1% of the total length); dorsum light greyish brown, with an indistinct dark neck collar and few dark blotches along posterior vertebral region; two pairs of light blotches on tail; venter yellowish beige, with dark outermost corners in each of ventrals and anterior subcaudals. A key to the Vietnamese and Chinese species of Calamaria is provided. Calamaria gialaiensis sp. nov. is the sixth species of Calamaria recorded from Vietnam.