The Tumen River is a river in Northeast Asia, flowing through parts of China, North Korea, and Russia. It originates from the Changbai Mountains in China and travels approximately 521 kilometers before emptying into the Sea of Japan. The river serves as a natural border between North Korea and China for a significant portion of its length. The Tumen River basin is known for its diverse ecosystems and rich biodiversity. It is home to various species of fish and wildlife, making it an important area for conservation. Additionally, the river plays a role in local economies, supporting fishing and agriculture in the surrounding regions.