This book explores the roles of Islam in Indonesia's foreign policy. Indonesia is a country with the world's largest Muslim community, where the political meaning of Islam is contested in the process of nation-building. Islam has come under increasing scrutiny by international relations scholars, particularly since Islamic extremism has become one of the major challenges to the post-Cold War world order. Therefore, it is important to research whether and how the religion has impacted the basic thinking and making of foreign policy in Indonesia. To contextualize the analysis, the study pays special attention to Indonesia's relations with Pakistan as a major case study.