Jon Lewis is a Research Fellow at the Program on Extremism at George Washington University, United States, where he studies the effects of leadership decapitation on terrorist organizations, the external operations of the Islamic State in Europe and the United States, and supporters of extremist groups in the United States.

Before joining the Program on Extremism, he worked as a research assistant at the International Institute for Counterterrorism (ICT) and the Combating Terrorism Center at West Point (CTC), where he co-authored a report on Islamic State-linked attacks and plots in Belgium. Jon Lewis holds a Masters in Homeland Security Policy from Rider University.