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The IUCN Red List of Threatened Species is the reference database for the extinction risk of animals, fungi and plants. This page is for researchers and research administrators who need to read its counts correctly, use its data within the terms of use, and cite it in the form IUCN asks for. Facts below come from the Red List’s own FAQ, background, terms-of-use and citation pages, checked on 2026-11-07 (see Sources).
What the IUCN Red List is
The Red List was established in 1964 and is described by IUCN as the world’s most comprehensive information source on the extinction risk of animals, fungi and plants. Each entry is an assessment of one taxon against a fixed set of categories and criteria. The Red List gives a measure of current extinction risk, not an estimate of when extinction will occur.
Who runs it and what it covers
IUCN runs the Red List. Assessors, usually species experts, prepare assessments; Red List Authorities review them; the IUCN Red List Unit checks them before publication. Sources include papers, books, reports, expert and indigenous knowledge, and citizen science. The site is updated a few times per year, and the footer of the current release reads “Version 2026-1”.
Covered taxa are animals, plants and fungi, at the level of species, subspecies, plant varieties and subpopulations (a subpopulation needs a species-level assessment first). Hybrids, domesticated taxa and micro-organisms are not included. Printed editions have ended, and national Red Lists are managed by each country.
Categories and criteria
Assessments follow the IUCN Red List Categories and Criteria: Version 3.1 (second edition, published in English, French, Spanish and Japanese). There are nine categories: Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC), Data Deficient (DD) and Not Evaluated (NE). Vulnerable, Endangered and Critically Endangered together are called “threatened”. Five criteria, based on geographic range, population size, population decline or increase, and extinction-probability analyses, place a taxon in a category. Least Concern taxa are included so that changes in the status of biodiversity can be tracked. Not Evaluated taxa are not shown on the Red List website. Regional assessments add Not Applicable and Regionally Extinct.
How many species have been assessed, and how many are threatened?
IUCN reports more than 175,900 species on the Red List, of which more than 49,500 are threatened with extinction. It also holds more than 3,000 subspecies and plant varieties and more than 30,000 regional assessments. More than 2 million species have been described, so fewer than 10% have been assessed. The counts therefore describe the assessed species only, not all life. IUCN’s stated goal is at least 260,000 species assessed and 142,000 reassessed. Share threatened varies by group, per IUCN’s background page:
| Group | Share threatened (IUCN) |
|---|---|
| Reef-building corals | 44% |
| Amphibians | 41% |
| Trees | 38% |
| Sharks and rays | 38% |
| Conifers | 34% |
| Mammals | 26% |
| Freshwater fishes | 26% |
| Birds | 11.5% |
Which species is the most critically endangered?
The Red List does not rank species within Critically Endangered, so no single species is officially “the most” critically endangered. Critically Endangered is one category. A Critically Endangered taxon may carry a Possibly Extinct or Possibly Extinct in the Wild tag, and “last seen” dates are recorded for Extinct, Extinct in the Wild and those tagged taxa. To list the Critically Endangered species for a group or place, use the site’s Advanced Search and filter by category.
How to search and download
- Open the IUCN Red List website (iucnredlist.org).
- Use the search box for a name, or choose Advanced Search to filter the data (the route IUCN names for finding and downloading data).
- Refine by category, such as Critically Endangered, and by the other filters offered.
- Open a species fact sheet for the assessment; the preferred citation sits at the top of each fact sheet.
- To save searches and download, register or sign in using Login/Register at the top right; download preferences are under Edit Profile.
Terms of use for researchers
From the Terms and Conditions of Use (version 3.1, June 2024):
- You may use, download and print data without prior permission solely for conservation or education purposes, scientific analyses and research (section 5).
- Commercial use needs written permission. IUCN defines it as use by or for a for-profit entity, or use that generates revenue (section 3). The category attached to each taxon may be freely viewed and queried.
- Do not repost or redistribute data in its original format, including through APIs, web downloads or public data archives (section 4). In research data management terms, raw Red List downloads should therefore not be deposited in a public repository.
- Give full acknowledgement and citation, including the version (section 6), and send IUCN an electronic copy, or two paper copies, of publications that use the data (section 5).
- Do not use superseded versions unless a specific analysis needs them (section 7).
How to cite the IUCN Red List
IUCN asks you to treat the Red List as an online journal: the journal title is “The IUCN Red List of Threatened Species”, the year is the volume and the version is the issue, for example The IUCN Red List of Threatened Species 2026(1). Use the preferred citation at the top of the species fact sheet. PDF versions have DOIs and should be cited using the citation on the PDF front page. In text, use the assessors and assessment date, for example “Ramirez-Chaves et al. (2015)”. Spatial data have their own pattern, for example: IUCN (International Union for Conservation of Nature) 2008. Vampyressa melissa (spatial data). The IUCN Red List of Threatened Species 2026(1). https://www.iucnredlist.org. Accessed on 09 July 2026.
Strengths and limits
- Strength: a single standard (Categories and Criteria v3.1) applied by expert assessors with review, with the evidence sources listed per assessment.
- Limit: under 10% of described species are assessed, and Not Evaluated taxa do not appear on the site.
- Limit: it measures current extinction risk, not timing, and the reassessment aim is every 5 to 10 years, so an assessment may predate recent change.
- Limit: data may not be redistributed or used commercially without permission.
Alternatives and related sources
| Source | Relation to the Red List |
|---|---|
| National Red Lists | Managed by each country; IUCN’s FAQ points to the National Red List site and notes BGCI ThreatSearch carries some. IUCN coordinates some regional projects (Europe, Mediterranean). |
| CITES | A trade regulation instrument, not an extinction-risk assessment; see CITES permits. |
| Convention on Biological Diversity | A treaty framework for conservation policy; see the Convention on Biological Diversity guide. |
For the disciplines that use these assessments, see what conservation biology is and what wildlife biology is.
FAQ
How many species have been assessed by the IUCN Red List?
More than 175,900 species, per IUCN’s background and FAQ pages (checked 2026-11-07), against more than 2 million described species.
How many species are threatened with extinction?
More than 49,500, meaning assessed as Vulnerable, Endangered or Critically Endangered.
What are the critically endangered species on the IUCN Red List?
They are the taxa assessed in the Critically Endangered category. The set changes with each update, so use Advanced Search filtered by category and group for the current list.
Which is the most critically endangered species?
The Red List does not rank within the category, so there is no official answer.
Can I use Red List data in my research?
Yes, without prior permission, for research, scientific analyses, conservation or education, provided you cite the version and do not redistribute the data in its original format.
Sources
- IUCN Red List, FAQ, checked 2026-11-07.
- IUCN Red List, Background and History, checked 2026-11-07.
- IUCN Red List, Terms and Conditions of Use, version 3.1, June 2024, checked 2026-11-07.
- IUCN Red List, Citing the IUCN Red List, checked 2026-11-07.
- IUCN Red List, Categories and Criteria v3.1, checked 2026-11-07.
