Harhorin (Хархорин), or Khara Khorum in Classical Mongolian, is a town in Övörhangay aymag, Mongolia. It was the "capital" of the Mongol Empire for 30 years.

The town on the Orhon River was constructed by Ögedei Khan in 1235. Persian merchants and Chinese craftmen were main habitants in the cosmopolitan empire. Although Harhorin is often said to be the capital of the Mongol Empire, the Mongol Khan lived in the movable palaces outside the city like other nomadic rulers. Harhorin served as the supply base for the actual "capital".

After Khubilai Khan moved the "capital" to Dadu, Harhorin was degraded to a provincial city. Although the Northern Yuan temporarily put the capital there, the subsequent strife between the Forty Mongols and Four Oyirad ruined it. Chinese invaders sacked and destroyed the city and massacred its inhabitants in 1388.

The ruins of Karakorum were discovered in 1889 by the Russian explorer N. M. Yadrinstev.

In 1585 Abadai Khan of the Khalkha built a Tibetan Buddhist monastery called Erdene Zuu (Erdeni Juu) there. Various construction materials were taken from the ruin to build this monastery.

In Mongolia some people favor relocating the national capital from Ulaanbaatar to Harhorin.