The redside dace (Clinostomus elongatus) is a species of ray-finned fish in the family Cyprinidae, found in the United States and Canada.

The redside dace is brightly coloured, with a wide red stripe extending from the head to the dorsal fin, running along the middle of the body.

Distinguishing it from other cyprinids, the species has a very large mouth and protruding lower jaw, which is an effective adaptation for capturing prey from below.

[7] The species favours slow-moving, cool, and clear headwaters of river systems, with copious overhanging riparian vegetation, especially grasses, forbs, and low shrubs.

The redside dace is listed as endangered in Indiana and as of February 20, 2009, also in Ontario, as threatened in Michigan, and as special concern in Wisconsin.