Siobhan Steel is a Fellow with the Transatlantic Defense and Security Program at the Center for European Policy Analysis (CEPA).

Steel is also the Council on Foreign Relations Robert A. Belfer International Affairs Fellow in European Security. Her research examines Europe's growing emphasis on sovereign capability and what it means for interoperability and transatlantic security cooperation.

Steel served at the US Department of Homeland Security (DHS) from 2017 to 2025, most recently as Deputy Director for Latin America and the Caribbean in the Office of International Affairs. In that role, she led regional engagement with foreign government counterparts and represented DHS in multilateral forums, including efforts related to the Los Angeles Declaration. Earlier at the department, she led an intelligence team focused on transnational organized crime and served as a strategic counterterrorism analyst covering terrorist travel and immigration trends across Asia and Latin America.

In the private sector, Steel served as Chief of Staff at BMNT Ltd, an advisory consultancy that helps bring commercial innovation into UK defense.