Since Hamas's attack on Israel last October 7, the term "settler colonialism" has become a center of political debate in the United States. Many progressives, academics, and student organizations justified the attack on the grounds that Israel is a settler colonial state, meaning that it was created on land taken from an indigenous people, and so can never be legitimate. The phrase was new to most Americans, and leading publications like the New York Times and the Atlantic have published articles explaining what it means. But the concept has been influential in academic and activist circles for years, shaping the way many young people think--not just about Israel and Palestine, but about the history of the United States and a host of political issues. Building on Adam Kirsch's October 2023 Wall Street Journal article on the topic, this short book is the first to examine the idea critically for a general readership. By exploring the most important writers, texts, and ideas in the field of settler colonial studies, Kirsch shows that it is really a new political ideology, aimed at delegitimizing not only Israel but also the United States, Canada, and Australia. He examines the sources of its appeal, which are spiritual as much as political, and how it turns indignation at past injustices into a source of new injustices today. As a compact and accessible introduction to one of the crucial political ideas of our moment, the book will speak to readers interested in the Middle East, American history, and today's most urgent cultural-political debates.