Gongmin (Korean: 공민; Hanja: 恭愍; 23 May 1330 – 27 October 1374), also known by his Mongolian name, Bayan Temür, was 31st ruler of Goryeo from 1351 to 1374. He was the second son of King Chungsuk.

Goryeo had been a semi-autonomous vassal state under the overlordship of the Mongol Yuan dynasty since the Mongol invasions of Korea in the 13th century. Starting with King Chungnyeol, prospective rulers of Korea married Mongolian princesses and were customarily sent to the Yuan Court, in effect, as hostages. As per this custom, King Gongmin spent many years in the Yuan court, being sent there in 1341, before ascending the Korean throne. He married a Mongolian princess who became Queen Indeok. The Yuan dynasty began to crumble during the mid-14th century, and was eventually conquered and replaced by the Ming dynasty in 1368.

With the disintegration of Yuan, which had forcibly allied the Korean peninsula since the 40 year long Mongol invasion of Korea of 1238, King Gongmin began efforts to reform Goryeo government. His first act was to remove all pro-Mongol aristocrats and military officers from their positions. These deposed people formed a dissident faction which plotted an unsuccessful coup against the king. High official Cho Il-sin even tried to take over the government, but this rebellion was put down by general Ch'oe Yŏng.

During the Mongol invasions of Korea, between the 1250s and the 1270s, the Mongols annexed the northern provinces of Korea and incorporated them into their empire as Ssangseong and Dongnyeong Prefectures. In 1356, the Goryeo army retook these provinces partly thanks to the defection of Yi Cha-ch'un, a minor Korean official in the service of the Mongols in Ssangseong, and his son, Yi Sŏng-gye. In addition, Generals Yi Sŏng-gye and Chi Yong-su led a campaign into Liaoyang.

Another issue was the question of land holdings. The land-grant system had broken down, and Mongol-favoured officials, along with a handful of landed gentry, owned the vast majority of agricultural landholdings, which were worked by tenant farmers and bondsmen. However, King Gongmin's attempt at land reform was met with opposition and subterfuge from officials who were supposed to implement his reforms, as they were landowners themselves.

The Wokou (Japanese pirates) were also a problem during King Gongmin's reign. Initially starting as 'hit-and-run' bandits, the Wokou evolved into well-organized military marauders raiding deep into the interior. Generals Ch'oe Yŏng and Yi Sŏng-gye were tasked to combat them.

Additionally, King Gongmin grappled with the Red Turban troops, who invaded Goryeo twice during his reign (first in 1359 and again in 1361). In 1361, the Red Turban troops occupied Kaesong for a short period of time. After Kaesong was recaptured by Generals Ch'oe Yŏng, Yi Sŏng-gye, Chŏng Se-un, and Yi Pang-sil, few Red Turban troops escaped with their lives.

During the reign of King Gongmin, a Goryeo diplomat, Mun Ikchŏm, stationed in China, managed to smuggle cotton seeds into Goryeo, introducing cotton cultivation to the Korean peninsula.