Cities exchange people, energy and goods with their local and global hinterlands9,10. Companies work with others across their value chains, near and far. Both interact with each other. We found that the top 200 cities with the largest greenhouse-gas emissions host the headquarters of 360 of the top 500 emitting companies. More than 50% of these cities and companies are in water-stressed areas, including Mexico City, Santiago, Beijing, Madrid, New Delhi, Rome, Istanbul in Turkey and Phoenix, Arizona.