Lists of endangered languages are mainly based on the definitions used by UNESCO.In order to be listed, a language must be classified as "endangered" in a cited academic source. Researchers have concluded that in less than one hundred years, almost half of the languages known today will be lost forever. The lists are organized by region.

An endangered language is a language that is at a risk of falling out of use, generally because it has few surviving speakers. If it loses all of its native speakers, it becomes an extinct language. UNESCO defines four levels of language endangerment between "safe" (not endangered) and "extinct":. Vulnerable; Definitely endangered; Severely endangered ...