This paper examines socio-historical roots of Southeast Asia’s Islamist terrorism. Specifically focusing on cases of terrorism in Indonesia, it deals with global, regional, and local factors that underline the emergence of “radical Islamism” as the roots of modern terrorism. Although there had been some connections between Southeast Asia’s militant Islamists to Afghanistan-based jihadists, an emphasis on the Al-Qaeda-centric paradigm as a framework for analyzing the rise of the region’s terrorism is over-exaggerated. This analytical emphasis tends to ignore the international, regional and local agencies outside Al-Qaeda as well as local political dynamics and socio-historical grounds that have contributed to the appearance of radical Islamism. Subscribing to Edward Said’s “travelling theory”, this paper argues that the idea of terrorism travels, not only from “person to person, from situation to situation, from one period to another” in a socio-historical vacuum, but also in response to specific historical and social changes. The idea of “radical Islamism” travels particularly from Afghanistan and elsewhere to Southeast Asia, especially Indonesia.