All Known Organizations Worldwide that Claim to be Working to Prevent Human Extinction:

Open invitation: Please recommend adding or modifying organizations

Existential risk institutions may raise awareness, conduct research, develop mitigation solutions and strategies, or advocate for policy changes and global cooperation to prevent human extinction.

Berkeley Existential Risk Initiative www.existence.org
Bulletin of Atomic Scientists https://thebulletin.org
Carnegie Climate Governance Initiative https://www.c2g2.net
Center for Human-Compatible Artificial Intelligence (CHAI) https://humancompatible.ai
Centre for the Study of Existential Risk (CSER) https://www.cser.ac.uk
Existential Risk Observatory https://www.existentialriskobservatory.org/
Extinction Rebellion http://www.rebellion.global
Future of Humanity Institute (FHI) https://www.fhi.ox.ac.uk/
Future of Life Institute (FLI) https://futureoflife.org
Garrick Institute for the Risk Sciences www.risksciences.ucla.edu
Global Catastrophic Risk Institute (GCRI) https://gcrinstitute.org
Global Challenges Foundation https://globalchallenges.org
Harvard-MIT Project on Existential Risk https://harvardmitxrisk.org/
Lifeboat Foundation https://lifeboat.com/ex/about
Machine Intelligence Research Institute (MIRI) https://intelligence.org/
NASA Planetary Science Division https://science.nasa.gov/solar-system
Nuclear Threat Initiative (NTI) https://www.nti.org/
OpenAI https://openai.com
Stanford Existential Risks Initiative (SERI) https://seri.stanford.edu
Swiss Existential Risk Initiative (CHERI) LINK https://effectivealtruism.ch/swiss-existential-risk-initiative#
UN Environment Montreal Protocol Ozone Secretariat https://ozone.unep.org
UN Framework Convention on Climate Change, Secretariat https://unfccc.int
US Federal Government Interagency Committee on Global Catastrophic Risk https://www.congress.gov/bill/117th-congress/senate-bill/4488/text
World Economic Forum www.weforum.org
Yale Existential Threats Initiative (YETI) https://www.yalexrisk.org