Together with the Tumen River to its east, and a small portion of Paektu Mountain, the Yalu forms the border between China and North Korea.

In Mandarin Chinese, yālù phonetically approximates the original Manchu word, but literally means "duck green", which was said to have been once the color of the river.

The other theory is that the river was named after the combination of its two upper branches, which were called "鴨" (Yā or Ap) and "綠" (Lù or R(or n)ok)", respectively.

The Yalu's most significant tributaries are the Changjin (장진강; 長津江), the Hochon (허천강; 虛川江), the Togro (독로강; 禿魯江) rivers from Korea and the Ai (or Aihe) (璦河) and the Hun (浑江) from China.

Many former fortresses are located along the river and the former capital of that kingdom was situated at what is now the medium-sized city of Ji'an along the Yalu, a site rich in Goguryeo-era relics.

[8] Wihwa Island on the river is historically famous as the place where, in 1388, General Yi Songgye (later Taejo of Joseon) decided to turn back his army southward to Kaesong in the first of a series of revolts that eventually led to the establishment of the Joseon dynasty.

[9] The river has been the site of several battles because of its strategic location between Korea and China, including: The southern side of the river was heavily industrialized during the period of Japanese rule (1910–1945), and by 1945 almost 20% of Japan's total industrial output originated in Korea.

During the Korean War, the movement of United Nations troops approaching the river, despite repeated warnings by China not to, precipitated massive Chinese intervention from around Dandong.

During the war the valley surrounding the western end of the river also became the focal point of a series of dogfights for air supremacy over North Korea, earning the nickname "MiG Alley" in reference to the MiG-15 fighters flown by the combined North Korean, Chinese, and Soviet forces.