The scaly sand darter (Ammocrypta vivax) is a species of freshwater ray-finned fish in the perch family, endemic to the southeastern United States. It is found in the coastal plain area of the Mississippi River basin, typically in medium-sized streams with slow currents over sandy substrates where it feeds on midge larvae and other small invertebrates. The slender body is semi-translucent, yellowish with a dozen or so dark bars. This fish has a wide range and is relatively common, and the International Union for Conservation of Nature lists it as a "least-concern species".