The tessellated darter (Etheostoma olmstedi) is a species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is native to Canada and the United States. It was formerly considered a subspecies of the johnny darter, which it greatly resembles in general appearance.

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