Nandus mercatus sp. nov. is described from the Musi River drainage in Sumatra. It differs from all congeners in having a combination of the following characters: body depth 43.0–43.2% SL, 15 pectoral-fin rays, 29–32 lateral line scales, 11–12 scale rows below the lateral line, and slightly concave predorsal profile. The characters that diagnose the genus are also reviewed and identified. Nandus is here diagnosed as having the following combination of characters: ectopterygoid toothed, posterodorsal corner of the subopercular not produced into a slender process and the second preural centrum with a distally bifurcate hemal spine.