Urbanization is set to play an ever greater role in the development of the Greater Mekong Subregion (GMS) countries, transforming their economies and providing support to green economic growth. With urbanization levels still averaging about 30% in GMS countries, gross domestic product contributions of towns and cities have already reached 50%–60%. By 2050, when urban areas are set to reach 64%–74%, urban gross domestic product will grow to an estimated 70%–80%. By consolidating and deepening development along existing corridors and improving environmental conditions, the GMS can prepare for future green growth.