The 21st century has been described as the ‘Asian Century.’ A dynamic hub in this rising Asia is the Southeast Asian region—encompassing diverse countries, peoples and cultures. ‘Changing Security Dynamics in South East Asia’ deliberates on Southeast Asian perspectives on security, the role of external powers—both current and also those that are rising, problems of religious fundamentalism and terrorism, challenges of maritime cooperation among countries abutting crucial world energy transit routes, advantages of regional, multilateral organizations in fostering cooperative behaviours, and India’s growing role and stakes in this region. The contributors point out that the primary security concerns confronting the region are often internal in nature. On the external front, they note the changing geo-political situation—due to the rise of China, a revitalized Japan, a more active Indian presence, along with the continued primacy of the United States. Stressing that these changes were accompanied by their own sets of opportunities and challenges, they express confidence in the ability of regional organizations like the Association of South East Asian Nations (ASEAN) to deal with the challenges. The waterways of the Southeast Asian region are vital routes for the transit of energy supplies feeding East Asian economic growth. Participants discussed ways to more effectively coordinate responses to the varied threats and challenges facing these waterways—including piracy, terrorism and transnational criminal networks.