Heather Williams

Director, Project on Nuclear Issues and Senior Fellow, Defense and Security Department
Williams

Dr. Heather Williams is the director of the Project on Nuclear Issues (PONI) and a senior fellow in the Defense and Security Department at the Center for Strategic and International Studies (CSIS). She is an affiliate with the MIT Center for Nuclear Security Policy, an associate fellow with the Project on Managing the Atom at the Harvard Kennedy School, and a senior associate fellow with the Royal United Services Institute in London. Dr. Williams is a member of the UN Secretary-General Advisory Board on Disarmament Affairs, and she has been a member of the Defense Science Board and the Department of State International Security Advisory Board. Before joining CSIS, Dr. Williams was a visiting fellow with the Project on Managing the Atom at the Harvard Kennedy School and a Stanton Nuclear Security fellow in the Security Studies Program at MIT. Until 2022, she was a senior lecturer (associate professor) at King’s College London and served as a specialist adviser to the House of Lords International Relations Committee. Dr. Williams has a PhD in war studies from King’s College London, an MA in security policy studies from the George Washington University, and a BA in international relations and Russian studies from Boston University.

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The Arsenal of Freedom Tour

Please join the CSIS Defense and Security Department for a conversation on the Secretary of War’s Arsenal of Freedom tour.

Event — January 22, 2026

Report Launch: Project Atom 2025

Please join the Project on Nuclear Issues for a launch event for the Project Atom 2025 report on escalatory risk in the Indo-Pacific. 

Event — December 10, 2025

Strategic Trends 2025

In a world where old nuclear guardrails are eroding and new rivalries are converging, Strategic Trends 2025 charts how the United States and its allies must navigate a disorderly, multi-adversary nuclear landscape and rethink deterrence for an unpredictable era.

Report by Nicholas Adamopoulos, Diya Ashtakala, Doreen Horschig, Lachlan MacKenzie, Catherine Murphy, Joseph Rodgers, Bailey Schiff, Pranay Vaddi, Heather Williams, and Reja Younis — November 18, 2025

Russia’s Latest Nuclear Saber-Rattling: Nuclear Testing?

President Putin’s instruction for Russian military and political leaders to begin “preparations for nuclear weapons tests” follows President Trump’s similar order last week, but also fits a wider pattern of nuclear saber-rattling tied to the ongoing war in Ukraine.

Critical Questions by Heather Williams and Lachlan MacKenzie — November 5, 2025

Can the United States Immediately Return to Nuclear Testing?

President Trump’s post raises technical questions about how and if the United States could “immediately” return to nuclear testing, and political considerations about the signaling behind nuclear testing and who would benefit most from a return to testing.

Critical Questions by Heather Williams — October 30, 2025