The largemouth bass is a carnivorous freshwater ray-finned fish in the Centrarchidae (sunfish) family, native to the eastern and central United States, southeastern Canada and northern Mexico. It is known by a variety of regional names, such as the widemouth bass, bigmouth bass, black bass, bucketmouth, largie, Potter's fish, Florida bass, Florida largemouth, green bass, bucketmouth bass, green trout, Gilsdorf bass, Oswego bass, LMB, and southern largemouth and northern largemouth.

Freshwater fish are fish species that spend some or all of their lives in bodies of fresh water such as rivers, lakes and inland wetlands, where the salinity is less than 1.05%. These environments differ from marine habitats in many ways, especially the difference in levels of osmolarity. To survive in fresh water, fish need a range of physiological adaptations.