Perca is the genus and species of fish referred to as perch or, sometimes, yellow perch, a group of freshwater fish belonging to the family Percidae. Perch, of which there are three species in different geographical areas, lend their name to a large order of vertebrates: the Perciformes, from the Greek perke meaning perch, and the Latin forma meaning shape.

Perch have "rough" or ctenoid scales. On the anterior side of the head are the maxilla and lower mandible for the mouth, a pair of nostrils, and two lidless eyes. On the posterior sides are the opercula, which are used to protect the gills. Also there is the lateral line system which is sensitive to vibrations in the water. They have a pair of pectoral and pelvic fins. On the anterior end of the fish, there are two dorsal fins. The first one is spiny and the second is soft. There is also an anal fin, which is also considered spiny, and a caudal fin. Also there is a cloacal opening right behind the anal fin. All perciform fish share the perch's general morphology.