Northeast Asia is a regional imaginary of limited capture among both academics and the general public. As a result, ongoing tensions relating to island claims, sea rights, borderlands, population mobilities, and resource access are too rarely considered from a Northeast Asian regional perspective. The region's parameters are also highly debated, with some conceptualizations restricted to Japan and the Korean Peninsula, while more expansive considerations include Russia, South Korea, North Korea, China, Japan, and Mongolia. We suggest that in addition to these countries, even maritime border zones in the Asia-Pacific and Arctic might be included as part of Northeast Asia's extent. In an effort to advance scholarly research on Northeast Asia, this special issue brings together articles that critically interrogate the region's political, economic, cultural, and environmental dynamics and conditions. Articles approach the region as a whole or employ specific case studies pertinent to relations within and/or between its composite states, subregions, and stakeholders. This introduction brings into relief the region's unique history as an inter-imperial frontier and its role as an understudied European, Asian, and North American borderland. These broad themes require consideration of Northeast Asia as a site of mass migrations, increasing environmental fragility, tentative geo-economic integration, and enduring geopolitical contestation. The editors of this special issue aim for this collection of articles to advance Northeast Asia as both a subject and frame for varied modes of geographic inquiry.