The reptile order that includes crocodiles, alligators, caimans, and gharials is Crocodilia.
Crocodilia contains three living families: Crocodylidae, the true crocodiles; Alligatoridae, the alligators and caimans; and Gavialidae, the gharial and false gharial. Although people often use “crocodile” loosely for the whole group, “crocodilian” is the clearer collective term.
These animals are semiaquatic predators with long snouts, powerful tails, armored skin, and eyes, ears, and nostrils positioned high on the head. Crocodilians are also archosaurs, making them the closest living relatives of birds. Their lineage extends back roughly 250 million years, while modern Crocodilia appeared in the Late Cretaceous, about 83.5 million years ago.
A common mix-up is treating Crocodilia as a family or confusing it with other reptile orders. Rhynchocephalia contains the tuatara, Testudines contains turtles and tortoises, and Squamata contains lizards and snakes. “Crocodylia” is also a long-used variant spelling, but Crocodilia is a valid and widely accepted form.