The spotted flagtail or dark-margined flagtail (Kuhlia marginata), is a species of flagtail native to fresh and brackish waters of islands of Southeast Asia and Oceania. It may also enter marine waters. It mostly occurs in sunny areas of rocky rivers at depths of from 1.5 to 3 m (4.9 to 9.8 ft). It can reach 17.9 cm (7.0 in) in standard length. This species is important to local commercial fisheries and is also a popular species for display in public aquaria.