Fundulus olivaceus is a species of fish in the family Fundulidae, the topminnows and North American killifishes. It is known by the common name blackspotted topminnow. It is native to the south-central United States, where it is known from the drainages of the Mississippi River from Illinois to the Gulf of Mexico and as far west as Galveston Bay.This fish has an elongate body up to 9.7 centimeters long.