South Korea–United States relations

Diplomatic relations between South Korea and the United States commenced in 1949. The United States helped establish the modern state of South Korea, officially the Republic of Korea, and fought on its UN-sponsored side in the Korean War (1950–1953). During the subsequent decades, South Korea experienced tremendous economic, political and military growth.

South Korea has a long military alliance with the United States, aiding the U.S. in every war since the Vietnam War, including the Iraq War. At the 2009 G20 London summit, then-U.S. President Barack Obama called South Korea "one of America's closest allies and greatest friends." In 1987, South Korea was among the first batch of countries to be designated as a major non-NATO ally. In June 2023, South Korean President Yoon Suk Yeol said that he had upgraded the country's alliance with the United States to one that is "nuclear-based" in the face of North Korea's growing military threat.

In 2023, President Yoon said that "Korea's experience shows us just how important it is for democracies to uphold solidarity. Korea will stand in solidarity with the free world. We will actively work to safeguard the freedom of the people of Ukraine and support their efforts in reconstruction" in a speech to the United States Congress.

By 2024, several security factors were shaping the alliance:

• Russia's war on Ukraine
• Gaza war
• China's growing influence on Asia-Pacific region
• China-Taiwan tension
• Increasing military threat from North Korea

South Korea is currently one of the most pro-American countries in the world. According to a 2018 Pew survey, 77% of South Koreans had a favorable view of the United States, while 21% had a negative view. According to a 2018 Gallup poll, 77% of Americans had a favorable view of South Koreans, while 22% had a negative view.