Goryeo under Mongol rule refers to the rule of the Mongol Empire and the Mongol-led Yuan dynasty over the Korean Peninsula from about 1270 to 1356. After the Mongol invasions of Korea and the capitulation of the Korean Goryeo dynasty in the 13th century, Goryeo became a semi-autonomous vassal state and compulsory ally of the Yuan dynasty for about 80 years. It has been referred to as a "son-in-law kingdom in the Mongol Empire." The ruling line of Goryeo, the House of Wang, was permitted to rule Korea as a vassal of the Yuan, which established the Branch Secretariat for Eastern Campaigns in Korea as an extension of Mongol supervision and political power. Members of the Goryeo royal family were taken to Khanbaliq, and typically married to spouses from the Yuan imperial clan, the House of Borjigin. As a result, princes who became monarchs of Goryeo during this period were effectively imperial sons in-law (khuregen). Yuan overlordship ended in the 1350s when the Yuan dynasty itself started to crumble and King Gongmin of Goryeo began to push the Yuan garrisons back.

Korea is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, now known as the Korean Demilitarized Zone. In 1948, two states declared independence, both claiming sovereignty over all of Korea: South Korea comprising its southern half and North Korea comprising its northern half. The region consists of the Korean Peninsula, Jeju Island, and minor islands near the peninsula. The peninsula is bordered by China to the north and Russia to the northeast, across the Amnok and Duman rivers. It is separated from Japan to the southeast by the Korea Strait.