Longest river with its entire drainage system in one country

The longest river that has its entire drainage system within one country is the Chang Jiang of China which measures 6,380 km (3,960 miles) long - the third longest river in the world, and the longest in Asia. The Yangtze, as it is also known, has its headwaters in the glaciers ofthe Qinghai-Tibetan plateau, heads eastwards across China's mainland and empties into the East China Sea.