The river flows in northeast Asia, on the border between China and North Korea in its upper reaches, and between North Korea and Russia in its last 17 kilometres before entering the Sea of Japan. The river forms much of the southern border of Jilin Province in Manchuria and the northern borders of North Korea's North Hamgyong and Yanggang provinces. Baekdu Mountain on the Chinese-North Korean border is the source of the river, as well as of the Yalu River.
The name of the river comes from the word '''', meaning "ten thousand". This river is badly polluted by the nearby factories of North Korea and China; however, it still remains a major tourist attraction in the area. In Tumen, Jilin, China, a riverfront promenade has restaurants where patrons can gaze across the river into North Korea. Russian name of river is ''Tumannaya''. It means ''foggy''.
Important cities on the river are Hoeryong, Namyang and Onsong in North Korea, and in China.
The Tumen has been used for years by North Korean refugees defecting across the Chinese border. Most refugees from North Korea during the 1990s famine crossed over the Tumen River, and most recent refugees have also used it.
Although the Tumen is heavily patrolled by armed guards of the DPRK, the river is considered the preferred way to cross into China because, unlike the swift and deep Yalu River which runs along most of the border between the two countries, the Tumen is shallow and narrow. "It is easily crossed in spots on foot or by swimming," according to a 2006 article in ''The New York Times''.
Defectors who wish to cross the Tumen often ignore its pollutants and dangerous border patrol, and spend weeks if not months or years waiting for the perfect opportunity to cross.
"Long, desolate stretches of the Chinese-North Korean border are not patrolled at all," according to ''The New York Times'' article.
Refugees seldom cross the Tumen into Russia because that government patrols its short stretch of the river more actively than China, and the refugees have no large ethnic Korean community in which to hide.