Prosotas aluta, the banded lineblue,[1][2] is a species of blue butterfly (Lycaenidae) found in Asia.

Race coelestis: Male upperside: shining bluish with a purple flush in certain lights.

Forewing: a transverse, subbasal, broad, dark, brownish-black, white-margined band from the subcostal to vein 1, a similar band along the discocellulars also extended to vein 1, an upper discal similar band from costa, curved a little outwards and stopping short at vein 3, followed by a postdiscal transverse series of dark spots which on the inner side are comparatively broadly, on the outer side very slenderly edged with white; succeeding which is a subterminal extremely slender series of transversely linear spots, a white line and a jet-black anteciliary line; cilia brown.

Hindwing: three transversely arranged dark brownish-black spots; transverse similarly coloured subbasal and discal bands, both bands inwardly and outwardly edged with slender white lines and the discal band greatly and irregularly widened in the middle, where superposed on the dark background is a snow-white transverse spot; beyond these are a postdiscal series of comparatively broad white lunules, a subterminal very slender white lunular line, a terminal white thread and a jet-black slender anteciliary line; cilia shining silky brown; tail brown tipped with white.

In Southeast Asia the butterfly ranges from Myanmar to southern Yunnan and southwards to Peninsular Malaysia, Borneo, Sumatra, Nias, northern Sulawesi, the Philippines, Thailand, Singapore, Vietnam, China, Nepal, Bhutan and Bangladesh.