The spotted sunfish (Lepomis punctatus), also known as a stumpknocker, is a member of the freshwater sunfish family Centrarchidae and order Centrarchiformes. The redspotted sunfish, redear sunfish and pumpkinseed sunfish are its closest relatives. Lepomis punctatus is olive-green to brown in color with black to reddish spots at the base of each scale that form rows of dots on the side. The scientific name punctatus refers to this spotted pattern. It was first described in 1831 by Valenciennes.

The spotted sunfish is a warmwater native of the Southeastern United States that inhabits areas of slow moving water. It is a benthic insectivore. Spotted sunfish do not commonly exceed 10 cm and a weight of 3 oz. It has some value as a pan fish and is occasionally caught by bream anglers. Spotted sunfish exhibit similar breeding behavior to other sunfishes. A single male guards a nest with multiple females. It is evaluated by the IUCN as a Least concern species and shows little danger of decline or high sensitivity to habitat changes. It has been suggested that it could be used as an indicator species, making it valuable to stream management. The spotted sunfish is a habitat generalist, but prefers complex habitats. It has not been established as an invasive species in other parts of the world.

Originally Lepomis punctatus and Lepomis miniatus were both classified as the same species Lepomis punctatus. Morphological differences and molecular evidence supported a significant difference in the eastern and western species of Lepomis punctatus. The species was divided into subspecies Lepomis punctatus punctatus in the east and Lepomis punctatus miniatus in the west. Later (1992) miniatus was elevated into its own species.

The spotted sunfish is a subtropical fish of the Southeastern United States found at latitudes of 41°N – 26°N. It is found in the Atlantic and Gulf Coastal drainages from the Cape Fear region in North Carolina to the Apalachicola River system in western Florida. The northernmost extent of its range is southern Tennessee. It is a warmwater fish and most abundant below the Fall Line. In Tennessee, Alabama and Georgia the spotted sunfish has not faced decline, but is vulnerable to decline in North Carolina. Its vulnerability has not been evaluated in South Carolina or Florida, but there is not evidence that it is threatened there. This range is fairly common to other Lepomis, though others have ranges farther northward or westward. No populations have been recorded outside of the native range. In older literature the range of the spotted sunfish may include that of the redspotted sunfish, which occurs farther westward into Texas and northward up the Mississippi river.

Spotted sunfish are largely insectivores throughout their entire lives, feeding on midge larvae and other immature insects. Most prey is benthic in origin, but insects at the surface are also preyed upon. Bream anglers have caught spotted sunfish using crickets or worms. They are also known to feed on microcrustaceans such as amphipods (Hyalella) and cladocerans. Spotted sunfish capture individual prey by suction feeding. Competition among various centrarchids is limited by physical difference in jaw mechanisms. For example, spotted sunfish and bluegill feed on similar prey items. Design of the lower jaw and therefore speed of capture varies between these two fishes; what one can easily capture the other cannot.

Because sunfish feed on similar prey items throughout their lives, competition occurs between young and adult fish. Centrarchids in general are top predators in many habitats, and a sunfish's main competitor may be other sunfish. Benthic organisms such as crayfish and other fish feed on eggs. In the closely related bluegill, cannibalism in areas of high nest density has been observed. This suggests that spotted sunfish could also be cannibalistic in similar situations. High densities of hydra were also linked to high mortality. Piscivores such as largemouth bass are predators of sunfish.

The spotted sunfish is a general habitat selector, but exhibits certain preferences. Juvenile and adults choose similar habitats, though younger fish sometimes show a preference for greater vegetation. It is a demersal fish that inhabits slow moving streams and rivers, swamps, and less brackish portions of estuaries. Spotted sunfish prefer heavily vegetated lake bottoms. Limestone, sand and gravel are preferred substrates. The Southeastern United States has acidic rain with a pH of 4.7-4.9. There is also a low carbonate hardness of Southeastern waters. This makes the area sensitive to acidification. Aquarists keeping sunfish have reported that they do best in neutral to high pH waters, in some extreme cases pH as high as 9.0 is observed. Acidification of their habitat could have negative impacts on the spotted sunfish.^{[citation needed]}

Spotted sunfish typically reach a length of 9.8 cm (3.86 in), with a record of 20 cm (7.87 in). A maximum weight of about three ounces is common.