June 26 is the 177th day of the year (178th in leap years) in the Gregorian calendar; 188 days remain until the end of the year.
221 – Roman emperor Elagabalus adopts his cousin Alexander Severus as his heir and receives the title of Caesar.
363 – Roman emperor Julian is killed during the retreat from the Sasanian Empire.
684 – Pope Benedict II is the last pope to require confirmation by the Byzantine emperor.
1243 – Mongols defeat the Seljuk Turks.
1295 – Przemysł II crowned king of Poland. The white eagle is added to the Polish coat of arms.
1460 – War of the Roses: Richard Neville, 16th Earl of Warwick, and Edward, Earl of March, land in England with a rebel army and march on London.
1483 – Richard III becomes King of England 1718 – Alexei Petrovich, Tsarevich of Russia, Peter the Great's son, mysteriously dies after being sentenced to death by his father.
1740 – A combined force of Spanish, free blacks and allied Indians defeat a British garrison at the Siege of Fort Mose near St. Augustine during the War of Jenkins' Ear.
1794 – French Revolution: Battle of Fleurus marks the first successful military use of aircraft .
1830 – William IV becomes king of Britain and Hanover.
1843 – Treaty of Nanking comes into effect, Hong Kong is ceded to the British.
1848 – End of the June Days Uprising in Paris.
1857 – The first investiture of the Victoria Cross in London.
1906 – The first Grand Prix motor race is held at Le Mans.
1909 – The Science Museum in London comes into existence.
1917 – World War I: American Forces begin to arrive in France. They will first enter combat in the Battle of Hamel on the 4th of July.
1918 – World War I: Allied forces under John J. Pershing and James Harbord defeat Imperial German forces under Wilhelm, German Crown Prince in the Battle of Belleau Wood.
1924 – American occupation of the Dominican Republic ends.
1927 – The Cyclone roller coaster opens on Coney Island.
1934 – United States President Franklin D. Roosevelt signs the Federal Credit Union Act.
1936 – Initial flight of the first practical helicopter.
1941 – World War II: Soviet planes bomb Hungary. Hungary declares war the next day.
1942 – The first flight of the Grumman F6F Hellcat.
1944 – World War II: San Marino, a neutral state, is mistakenly bombed by the RAF leading to 35 civilian deaths.
1944 – World War II: The Battle of Osuchy in Poland, one of the largest battles between Nazi Germany and Polish resistance ends with the defeat of the latter.
1945 – The United Nations Charter is signed by 50 Allied nations in San Francisco, California.
1948 – Cold War: The first supply flights are made in response to the Berlin Blockade.
1955 – The South African Congress Alliance adopts the Freedom Charter.
1959 – Swedish boxer Ingemar Johansson becomes world champion of heavy weight boxing, by defeating American Floyd Patterson.
1960 – Madagascar gains its independence from France.
1963 – Cold War: U.S. President John F. Kennedy gave his 'Ich bin ein Berliner' speech, underlining the support of the United States for democratic West Germany after Sovietsupported East Germany erected the Berlin Wall.
1974 – The Universal Product Code is scanned for the first time at a supermarket in Ohio.
1975 – Two FBI agents and a member of the American Indian Movement are killed in a shootout on the Pine Ridge Indian Reservation in South Dakota;
1977 – Elvis Presley held his final concert in Indianapolis, Indiana.
1995 – Hamad bin Khalifa Al Thani deposes his father Khalifa bin Hamad Al Thani, the Emir of Qatar.
1997 – The U.S. Supreme Court rules that the Communications Decency Act violates the First Amendment to the United States Constitution.