The warmouth (Lepomis gulosus) is a freshwater fish of the sunfish family (Centrarchidae) that is found throughout the eastern United States.

[5] Three to five reddish-brown streaks extend from the eyes,[4] whose irises are reddish, a feature most pronounced in breeding males,[6] with a red dot present on the otherwise black opercular flaps, outlined in yellow.

[8] These fish are typically 4 to 10 inches (10 to 25 centimetres) long, but can grow to over one foot (30 cm) in length, and reach 2.25 pounds (1.02 kg).

[4] The warmouth is occasionally confused with the rock bass (Ambloplites rupestris) or green sunfish (Lepomis cyanellus), both of which share its relatively large mouth and heavy body.

The largest factor affecting warmouth density and biomass in Florida's lakes is the availability of aquatic macrophytes, which allows the fish to ambush prey and use as areas to spawn.

[13] The primary diet of young warmouth is microcrustaceans and aquatic insect larvae, whereas larger specimens tend to mainly consume crayfish, freshwater shrimp, isopods,[8] and other small fish.

The species known to hybridize with it are the green sunfish (L. cyanellus) and the bluegill (L. macrochirus), as well as the largemouth bass (Micropterus salmoides) and the black crappie (Pomoxis nigromaculatus).

The International Game Fish Association (IGFA) all tackle world record for the species stands at 1.10 kg (2 lb 7 oz) caught in Holt, Florida, in 1985.