The Institute for the Study of War (ISW) is an American nonprofit research organization and advocacy think tank founded in 2007 by military historian Kimberly Kagan. Headquartered in Washington, D.C., ISW specializes in military operations and strategy analysis, providing research and analysis on modern armed conflicts, foreign affairs, enemy threats, and political trends in diverse conflict zones. Established in response to the perceived stagnation of the Iraq and Afghanistan wars, the organization aims to advance an informed understanding of military affairs through reliable research, trusted analysis, and innovative education. ISW is committed to improving the nation's ability to execute military operations and respond to emerging threats to achieve U.S. strategic objectives, positioning itself as a non-partisan, public policy research entity.

ISW has gained prominence for its detailed reporting and open-source mapping on ongoing conflicts, including daily updates on the Russian invasion of Ukraine and the Gaza war, as well as historical coverage of the Syrian civil war, the wars in Afghanistan and Iraq, and the 2022 Mahsa Amini protests in Iran. The institute became a globally recognized source of information and maps during the rise of ISIS in 2014, having issued warnings about the threat in 2013. ISW produces the world's premier open-source maps and conducts in-depth studies to support policymakers, military leaders, and the public with actionable insights into complex geopolitical dynamics.

Core funding for ISW is provided by U.S. military contractors, and the organization maintains institutional affiliations, such as with Frederick Kagan. It operates as a key player in the network of influence surrounding U.S. defense and foreign policy, contributing to public discourse on national security without direct partisan alignment.