- 479 BC 27 Aug The invasion of Greece by Persian emperor Xerxes is defeated by Pausanias at the Battle of Plataea.
- 1928 27 Aug The Kellogg-Briand Pact condemns 'recourse to war for the solution of international controversies'.
- 1979 27 Aug Elizabeth II's cousin, Lord Louis Mountbatten, is killed by an IRA bomb on his boat in Ireland.

