March 15: Saint Patrick's Day (observed, 2008); National Day in Hungary, Hōnen Matsuri in Japan.
- 44 BC – Dictator Julius Caesar of the Roman Republic was stabbed to death by Marcus Junius Brutus and several other Roman senators on the Ides of March.
- 1311 – The Catalan Company defeated Walter V of Brienne in the Battle of Halmyros and took control of the Duchy of Athens, a Crusader state in Greece.
- 1877 – Cricketers representing England and Australia began the first match in Test cricket at the Melbourne Cricket Ground in Melbourne, Victoria, Australia.
- 1917 – Tsar Nicholas II of Russia (pictured) was forced to abdicate in the February Revolution, ending three centuries of Romanov rule.
- 1939 – Nazi German troops began their occupation of Czechoslovakia and established the Protectorate of Bohemia and Moravia.
- 1988 – Iran–Iraq War: Iraqi forces began attacking the Kurdish town of Halabja with chemical weapons, killing up to 5,000 people.