A sunfish is a type of fish that belongs to the family of ray-finned fish called Cyprinodontiformes. They are also known as sunny, and they live in freshwater habitats such as ponds, lakes, rivers, and streams. Sunfish can grow up to 30 cm long and have a characteristic dorsal fin that resembles the shape of a sun. Some species of sunfish are popular among anglers for their sporting qualities while others are kept in aquariums as pets.