Toad can refer to a number of species of amphibians.

A distinction is often made between frogs and toads on the basis of their appearance, prompted by the convergent adaptation among so-called toads to dry environments, which often entails a brown skin for camouflage that is also dry and leathery for better water retention. Many so-called toads also burrow, which requires further specific adaptations. However, since these adaptations merely reflect the environment a species has adapted to, they offer no reliable guidance as to what other species it evolved from. Since taxonomy is meant to only reflect these evolutionary relationships, the aforementioned distinction of frogs and toads gives no clue to their classification.

For instance, many members of the families Bombinatoridae, Discoglossidae, Pelobatidae, Rhinophrynidae, Scaphiopodidae, and some species from the Microhylidae family are commonly called "toads". However, the only family exclusively given the common name "toad" is Bufonidae, the "true toads". Some "true frogs" of the genus Rana, have also adapted to burrowing habits, while the species within the toad genus Atelopus are conversely known by the common name "harlequin frogs."

The type species of the family Bufonidae is the Common Toad, Bufo bufo, and around it cluster a large number of species of the same genus and some smaller genera. B. bufo is a tailless amphibian of stout build with a warty skin and any animal that shares these characteristics is liable to be called a toad, regardless of its location in formal taxonomy.

Almost all toads of the family Bufonidae have two lumps on either side of the back of their head, called the parotid glands. These glands contain a poison, which oozes out if the toad is stressed. Some, like Cane Toad Bufo marinus, are more toxic than others. Some "psychoactive toads" such as the Colorado River Toad Bufo alvaris, have been used recreationally for the effects of the bufotoxin, by either smoking their skin secretions or eating boiled toads.

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