Harqin Left Wing Mongolian Autonomous County (), also abbreviated as Harqin County or Kazuo County, is a Mongolian autonomous county in the west of Liaoning province, China. It is under the administration of Chaoyang City, to the northeast, and has a population of 346,133 (2020) residing in an area of . Formerly known as Harqin Left Wing Banner ().
Harqin Left Wing is divided into 2 subdistricts, 14 towns and 5 townships.