Alligators eat almost anything, but primarily consume fish, birds, turtles, mammals and amphibians. Hatchlings however are restricted to smaller prey items like invertebrates. Insects and larvae, snails, spiders and worms make-up a big portion of a hatchling's diet. They will also eat small fish at any opportunity. As they grow, they gradually move onto larger fish, mollusks, frogs and small mammals like rats and mice. Sub adult alligators take a larger variety of prey; ranging from snakes and turtles to birds and moderate sized mammals like raccoons and pets.

Once an alligator reaches adulthood, any animal living in the water or coming to water to drink is potential prey. Adult alligators will eat razorbacks, deer, domestic animals including cattle and sheep, and are often known to kill and eat smaller alligators. Larger male alligators have been known to take down Florida panther and bears, making the American alligator the apex predator throughout its distribution.

The alligator's greatest value to the marsh and the other animals that inhabit it are the "gator holes" that many adults create and expand on over a period of years. An alligator uses its mouth and claws to uproot vegetation to clear out a space; then, shoving with its body and slashing with its powerful tail, it wallows out a depression that stays full of water in the wet season and holds water after the rains stop. During the dry season, and particularly during extended droughts, gator holes provide vital water for fish, insects, crustaceans, snakes, turtles, birds, and other animals in addition to the alligator itself.