The United States expedition to Korea, known in Korea as the Shinmiyangyo (Korean: 신미양요; Hanja: 辛未洋擾; lit. "Western Disturbance in the Shinmi Year (1871)") or simply the Korean Expedition, was the first American military action in Korea and took place predominantly on and around Ganghwa Island in 1871.

The reason for the presence of the American land and naval force in Korea was to support an American diplomatic delegation sent to negotiate trade and political relations with the peninsular nation led by the American ambassador to China, Frederick Low, to ascertain the fate of the merchant ship General Sherman, which had gone missing while visiting to Korea in 1866. However, according to a National Interest article, Low's own records indicated the punitive campaign was motivated by a need to demonstrate American power over what he considered to be a weaker nation. Previously, the American commanders had felt entitled to be able to "peacefully" enter Korean waters for survey and trade using heavily armed warships and had ignored repeated diplomatic requests to respect Korean sovereignty.In 1871, the United States sent Low along with the U.S. Navy's Asiatic Squadron to Korea to both investigate the General Sherman's disappearance and also attempt to convince the Koreans in opening up trade relations. The Korean officials however made it clear to Low that they were not interested in a trade treaty.

When Korean shore batteries attacked two American warships on 1 June down the Han River, Low decided to attack the forts unless the Koreans had formally apologized for the riverside ambush. However Korean officials sent letters holding the Americans as responsible for breaking their country's laws through unlawfully sending armed warships into their territorial waters, and also finally explaining to Low of what had similarly happened to the General Sherman.

The governor of Ganghwa also sent what Low described as a "few worthless articles"—three cows, fifty chickens and a thousand eggs—in an effort to de-escalate things. The Americans rejected the offer. Instead a punitive campaign was launched after the commanding American admiral failed to receive an official apology from the Koreans that they felt they were owed. The isolationist nature of the Joseon dynasty government and the imperial nature of the Americans to not recognise Korea's set policies, changed a diplomatic expedition into an armed conflict. On 10 June, about 650 Americans landed and captured several forts, killing over 200 Korean troops with a loss of only three American soldiers dead. Korea continued to refuse to negotiate with the United States until 1882.