The March First Movement was a series of protests against Japanese colonial rule that was held throughout Korea and internationally by the Korean diaspora beginning on March 1, 1919. Protests were largely concentrated in March and April of that year, although related protests continued until 1921. In South Korea, the movement is remembered as a landmark event of not only the Korean independence movement, but of all of Korean history.

The protests began in Seoul, with public readings of the Korean Declaration of Independence in the restaurant T'aehwagwan [ko] and in Tapgol Park. The movement grew and spread rapidly. Statistics on the protest are uncertain; there were around 1,500 to 1,800 protests with a total of around 0.8 to 2 million participants. The total population of Korea at the time was around 16 to 17 million. Despite the peaceful nature of the protests, they were frequently violently suppressed. One Korean estimate in 1920 claimed 7,509 deaths and 46,948 arrests. Japanese authorities reported much lower numbers, although there were instances where authorities were observed destroying evidence, such as during the Jeamni massacre. Japanese authorities then conducted a global disinformation campaign on the protests. They promoted a wide range of narratives, including outright denial of any protests occurring, portraying them as violent Bolshevik uprisings, and claiming that Koreans were in need of the benevolent rule of Japan. These narratives were publicly challenged by sympathetic foreigners and by the Korean diaspora.

The movement did not result in Korea's prompt liberation, but had a number of significant effects. It invigorated the Korean independence movement and resulted in the creation of the Korean Provisional Government. It also caused some damage to Japan's international reputation and caused the Japanese colonial government to grant some limited cultural freedoms to Koreans under a series of policies that have since been dubbed "cultural rule [ja; ko]". Furthermore, the movement went on to inspire other movements abroad, including the Chinese May Fourth Movement and Indian satyagraha protests.

The anniversary of the movement's start has been celebrated since, although this was largely done in secret in Korea until its liberation in 1945. In South Korea, it is a national holiday. The North Korean government initially celebrated it as a national holiday, but eventually demoted it and now does not evaluate the movement's significance similarly. It now promotes writings about the event that seek to emphasize the role of the ruling Kim family in the protests.

In 1910, Japan formally annexed Korea. Japanese rule was initially especially tight. Japan took control over Korea's economy, and began a process of Japanization: forced cultural assimilation. Land was confiscated from Koreans and given to Japanese people, and economic and administrative systems were created that were systemically discriminatory. Resistance was violently suppressed, and freedom of speech and press were tightly controlled.

Japanese colonial policies mandated that Koreans send increasingly significant portions of their economic output to Japan, for what was seen as inadequate compensation. This caused a significant decline in the quality of life for many farmers and laborers, who began publicly protesting their treatment. In 1916, there were 6 strikes with 362 participants. In 1917, there were 8 strikes with 1,128, and by 1918 there were 50 strikes with 4,442. Historians of the National Institute of Korean History argue that this reflected increasing discontent in Korea around the time of the movement.

Japan had been successfully rapidly industrializing since the late 19th century. Around this time, Western theories surrounding social Darwinism and colonial civilizing missions gained significant traction in Japan. These theories were often used to justify and promote Japanese colonialism. The devastation during the 1914–1918 First World War was a shock to many, and motivated intellectuals in Korea and around the world to discuss liberal reforms, especially anti-colonialism, and ideals that would serve to discourage future such conflicts.

After the end of the war in 1918, United States President Woodrow Wilson announced his vision for establishing peace and the new world order. This vision was dubbed the Fourteen Points, and included the right of national self-determination. Koreans who learned of Wilson's vision were inspired, and interpreted it as signaling support for their independence movement. Their sympathy to the U.S. and the Allies reportedly greatly increased.