Alligator mississippiensis, commonly known as the American alligator, is native to the southeastern United States. Its geographical distribution includes states such as Louisiana, Florida, Georgia, Alabama, Mississippi, South Carolina, North Carolina, Texas, and parts of Oklahoma and Arkansas.

The American alligator typically inhabits freshwater environments such as ponds, marshes, wetlands, rivers, lakes, and swamps. The preferred climate for this species is subtropical to tropical, characterized by warm temperatures and high humidity.

Alligator mississippiensis is a keystone predator within its ecosystem, playing a crucial role in controlling the population of various prey species, including fish, birds, and small mammals. It creates 'gator holes' which provide habitat for other wildlife, especially during dry periods. The species adapts to its environment by being able to regulate its body temperature through behavioral thermoregulation.