The United States Army Military Government in Korea (USAMGIK) was the official ruling body of the southern half of the Korean Peninsula from 9 September 1945 to 15 August 1948.

The country during this period was plagued with political and economic chaos, which arose from a variety of causes. The after-effects of the Japanese occupation were still being felt in the occupation zone, as well as in the Soviet zone in the north. Popular discontent stemmed from the United States' military government's support of the Japanese colonial government; then once removed, keeping the former Japanese governors on as advisors; by ignoring, censoring, and forcibly disbanding the functional and popular People's Republic of Korea (PRK); and finally by supporting United Nations elections that divided the country. The U.S. administration refused to recognize the Provisional Government of the Republic of Korea, despite the South Korean government considering it their predecessor since 1987.

In addition, the U.S. military was largely unprepared for the challenge of administering the country, arriving with no knowledge of the language or political situation. Thus, many of their policies had unintended, destabilizing effects. Waves of refugees from North Korea (estimated at 400,000)  and returnees from abroad caused further turmoil