The rhinoceros commonly called rhino for short; plural can be either rhinoceros or rhinoceroses) ("rhinoceros" is derived from the Greek words rhino, meaning nose, and ceros, meaning horn; hence "horn-nosed") is any of five surviving species of odd-toed ungulates in the family Rhinocerotidae. All five species are native to Africa, the Middle East, and southern Asia. Most species of rhino are endangered. Rhinoceros is also one of the genera in this family.

The family is characterised by: large size (one of the few remaining megafauna surviving today) with all of the species capable of reaching one tonne or more in weight; The rhino is prized for its horn. Not a true horn, it is made of thickly matted hair that grows from the skull without skeletal support. herbivorous diet; and a thick protective skin, 1.5-5 cm thick, formed from layers of collagen positioned in a lattice structure. Rhinoceros also have acute hearing and sense of smell, but poor eyesight over any distance. Most rhinoceros live to be about 50 years old or more. A male rhinoceros is called a bull, a female a cow, and the young a calf; the collective noun for a group of rhinoceros is "crash".

A powerful rhinoceros, though herbivorous, is arguably one of the deadliest creatures upon the earth to humans. In India and Nepal, rhinos cause the greatest number of wildlife-related human deaths each year, surpassing those caused by tigers and leopards. They have even been known to charge working elephants carrying tourists through the jungles. Much like other animals, they are most dangerous when in the presence of their young.

Either a rhinoceros or a unicorn is called a "monoceros" (meaning an animal with one horn).