- The United Nations General Assembly holds its first meeting in London, England.
- The United States Navy begins Operation Highjump, a military expedition to Antarctica led by Admiral Richard E. Byrd.
February 2
- Juan Perón is elected President of Argentina, beginning a nearly ten-year dictatorship.
March 5
- Winston Churchill delivers the "Iron Curtain" speech, warning of the growing threat of communism in Eastern Europe.
March 11
- The Nuremberg trials of Nazi war criminals begin in Nuremberg, Germany.
April 9
- The International Monetary Fund (IMF) is established to provide financial assistance to countries in need.
May 16
- The first Cannes Film Festival is held in Cannes, France.
June 26
- The United States Army Air Forces' B-29 bomber Enola Gay drops the first atomic bomb on Hiroshima, Japan, resulting in the deaths of an estimated 140,000 people.
July 16
- The first Bikini Atoll nuclear test is conducted by the United States Navy, detonating an atomic bomb 520 feet below sea level and creating a radioactive mushroom cloud.
August 6
- The United States Army Air Forces' B-29 bomber Bockscar drops the second atomic bomb on Nagasaki, Japan, resulting in the deaths of an estimated 74,000 people.
August 14
- The Emperor of Japan Hirohito announces Japan's surrender, ending World War II.
August 28
- The first Indonesian National Independence Congress is held in Jakarta, marking the beginning of Indonesia's struggle for independence from the Netherlands.
September 2
- The surrender of Japan is signed aboard the USS Missouri in Tokyo Bay, officially ending World War II.
October 24
- The United Nations charter is ratified, bringing the United Nations into existence.
December 11
- UNICEF (the United Nations Children's Fund) is established to provide emergency aid to children around the world.
December 19
- Ho Chi Minh declares the independence of Vietnam from France, marking the beginning of the First Indochina War.