A new species, Hapalogenys merguiensis, currently known only from Andaman Sea, is described from the holotype and five paratypes. This species is most similar to H. nitens Richardson, 1845, in overall appearance of body, as well as in having a single notched dorsal fin, poorly developed papillae on chin and dark brownish body color with two oblique dark bands curved posteriorly. However, it differs from H. nitens, from which it is also geographically separated, in a combination of several meristic and morphometric characters. Hapalogenys merguiensis n. sp. has the following diagnostic characters: dorsal fin rays XI, 14; anal fin rays III, 9 or 10; pored lateral line scales 39–42; gillrakers 5–7 12–14; scales above lateral line 9 or 10, below 18–20; no scales on maxilla; eye diameter more than approximately one-quarter head length; 10 pores on and behind chin; a cluster of very short dense papillae on fleshy lower lip; head and body generally dark brownish and two indistinct oblique bands on body, first descending from nape to behind pectoral fin and second from base of anterior second or third dorsal fin spines and soft dorsal fin base, curving posteriorly through lateral line to soft anal fin and caudal peduncle (one whitish or indistinct whitish brown, oblique band, curving posteriorly and becoming wider, from base of the first three dorsal fin spines to anus and spinous anal fin base); dark posterior margin absent from soft dorsal and anal fins but narrowly present on caudal fin; a procumbent spinelike process (exposed tip of first pterygiophore) at origin of dorsal fin.