Khalkhin Gol

The Khalkh River (also spelled as Khalkha River or Halaha River; Халх гол; Ha-la-ha; Ha-lo-hsin Ho) is a river in eastern Mongolia and northern China's Inner Mongolia region. The river is also referred to with the Mongolian genitive suffix -iin as the Khalkhin Gol, or River of Khalkh.

The river's source is the western slopes of the Greater Khingan mountains of Inner Mongolia. In its lower course, it forms the boundary between China's Inner Mongolia, and the Mongolian Republic until around 48.03318°N, 118.13429°W, the river splits into two distributaries. The left branch (the Halh River proper) flows into the Buir Lake at 47.89556°N, 117.83556°W; discharge from that lake at 47.95001°N, 117.81427°W) is known as the Orshuun Gol (Оршуун гол, ). The right branch, known as the Shariljiin Gol (Шарилжийн гол) flows directly into the Orshuun Gol at 48.06989°N, 117.75543°W. Orhuun connects the Buir Lake with the Hulun Lake. The Chinese–Mongolian border then follows the Shariljiin Gol for about an equal distance.

From May to September 1939, the river was the site of the Battles of Khalkhin Gol, the decisive engagement of the Soviet-Japanese border conflicts. Soviet and Mongolian forces defeated the Japanese Kwantung Army.