The following 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. 
- Afro-Eurasian languages
- African languages
- Eurasian languages
- Asian languages
- European languages
- Russian languages
- Australian languages
- North and South American languages
- List of endangered languages in North America
- List of endangered languages in South America
- Pacific languages
SIL Ethnologue (2005) lists 473 out of 6,909 living languages inventorized (6.8%) as "nearly extinct", indicating cases where "only a few elderly speakers are still living"; this figure dropped to 6.1% as of 2013.
In order to judge if a language is endangered, the number of speakers is less important than their age distribution. There are languages in Indonesia reported with as many as two million native speakers alive now, but all of advancing age, with little or no transmission to the young. On the other hand, while there are only 30,000 Ladin speakers left, almost all children still learn it as their mother tongue, thus Ladin is not currently endangered. Similarly, the Hawaiian language has only about 1,000 speakers but it has stabilized at this number, and there is now school instruction in the language, from preschool through the 12th grade. Thus the language is classified as merely vulnerable.
While there are somewhere around six or seven thousand languages on Earth today, about half of them have fewer than about 3,000 speakers. Experts predict that even in a conservative scenario, about half of today's languages will become extinct within the next fifty to one hundred years.