The Dangqu (Chinese: 当曲, p Dāngqū) or Dam Chu (Tibetan: འདམ་ཆུ, w 'Dam Chu, lit. "Marshy River") is a 234 km (145 mi) river in the Qinghai province of the People's Republic of China. It runs from its source in an eastern offshoot of the Tanggula Mountains (唐古拉山), receives its main tributary the Buqu (布曲), and has a confluence with the Ulan Moron, where the Tongtian River is formed. The Dangqu has been discovered to be the actual headwater of the Yangtze River under modern criteria, although the nearby Ulan Moron or Tuotuo was traditionally regarded as the primary river of the two.^[1]

Traditionally, the Dangqu—sometimes under the name Akdam, Akedamuqu, or A-ko-ta-mu-ch'ü—and the Buqu were both regarded as tributaries of the Garqu (尕尔曲), then known as the Moron Us (Mongolian: Mörön Us or Маруй-Ус, Maruy-Us; 木鲁乌苏河, p Muluwusu He) or Dequ (Дечу, Deču). Under modern criteria, the Garqu is instead considered to be a tributary of the Buqu.

34°05′32″N 92°54′48″E / 34.0921°N 92.9132°E / 34.0921; 92.9132