Wikipedia:Selected anniversaries/June 26
- 1409 - Western Schism: The Catholic church is led into a double schism as Petros Philargos is crowned Pope Alexander V after the Council of Pisa, joining Pope Gregory XII in Rome and Avignon Pope Benedict XIII in Avignon.
- 1940 - Under the Molotov-Ribbentrop Pact, the Soviet Union gave Romania an ultimatum requiring it to cede territory.
- 1945 - The United Nations Charter was signed in San Francisco, California.
- 1959 - The Saint Lawrence Seaway, a system of canals connecting the Great Lakes to the Atlantic Ocean, was officially opened.
- 1963 - John F. Kennedy uttered "Ich bin ein Berliner."