What role do nationalism and popular protest play in China's foreign relations? Chinese authorities permitted anti-American demonstrations in 1999 but repressed them in 2001 during two crises in U.S.-China relations. Anti-Japanese protests were tolerated in 1985, 2005, and 2012 but banned in 1990 and 1996. Protests over Taiwan, the issue of greatest concern to Chinese nationalists, have never been allowed. To explain this variation, Powerful Patriots identifies the diplomatic as well as domestic factors that drive protest management in authoritarian states. Because nationalist protests are costly to repress and may turn against the government, allowing protests demonstrates resolve and makes compromise more costly in diplomatic relations. Repressing protests, by contrast, sends a credible signal of reassurance, facilitating diplomatic flexibility. Powerful Patriots traces China's management of dozens of nationalist protests and their consequences between 1985 and 2012.