An endangered species is a species (a population) of animals, plants or other organisms that is in danger of becoming extinct. This could happen because there are few of that animal left, its predators have grown in number, or the climate that it lives in is changing, or the places it lives in have been destroyed. The World Conservation Union (IUCN) has worked out that endangered species are 40% of all organisms.

Many countries have laws to protect these plants and animals. These laws, if obeyed, can save species by stopping hunting, land development or making parks and reserves. Poaching and other illegal activities, however, can still destroy them.

Only a few plants and animals at risk of extinction, mostly vertebrates, are put on the lists and get legal protection. Many more species become extinct, or will become extinct, without people knowing about it.