A new species of triplefin, Enneapterygius niue, is described on the basis of three specimens from Niue and Samoa. The new species is a medium-sized species of barred Enneapterygius, characterized by 13–15 spines in the second dorsal fin, 18–20 anal-fin soft rays, 14–19 + 16–20 lateral-line scales, 33–36 total lateral scale rows, eye diameter 94–128, preorbital 50–75, body depth 176–206, preanal fin length 483–538 (last four measures in thousandths of SL), sides of body with a pattern of two short and five complete bars, pectoral-fin base with a vertical dark bar, preorbital with an oblique dark band, dorsal fins pale except for a dusky base, anal fin dark grey in male and with four oblique brown bands in female, pelvic fins white, and caudal fin pale. The new species is compared with similar species. A revised key to the species of Enneapterygius in the Indo-Australian Archipelago and the western Pacific is presented
