March 17 is the 76th day of the year (77th in leap years) in the Gregorian calendar. There are 289 days remaining until the end of the year.
- 45 BC – In his last victory, Julius Caesar defeats the Pompeian forces of Titus Labienus and Pompey the Younger in the Battle of Munda.
- 180 – Marcus Aurelius dies leaving Commodus the sole emperor of the Roman Empire.624 – Led by Muhammad, the Muslims of Medina defeat the Quraysh of Mecca in the Battle of Badr.
- 1776 – American Revolution: British forces evacuate Boston, Massachusetts, ending the Siege of Boston, after George Washington and Henry Knoxplace artillery in positions overlooking the city.
- 1780 – American Revolution: George Washington grants the Continental Army a holiday "as an act of solidarity with the Irish in their fight for independence".
- 1805 – The Italian Republic, with Napoleon as president, becomes the Kingdom of Italy, with Napoleon as King.
- 1948 – In Benelux, France, and the United Kingdom sign the Treaty of Brussels, a precursor to the North Atlantic Treaty establishing NATO.
- 1969 – Golda Meir becomes the first female Prime Minister of Israel.
- 1970 – My Lai Massacre: The United States Army charges 14 officers with suppressing information related to the incident.
- 1985 – Serial killer Richard Ramirez, aka the "Night Stalker", commits the first two murders in his Los Angeles, California murder spree.
- 1992 – Israeli Embassy attack in Buenos Aires: Suicide car bomb attack kills 29 and injures 242.
- 1992 – A referendum to end apartheid in South Africa is passed 68.7% to 31.2%.
- 2000 – More than 800 members of the Ugandan cult Movement for the Restoration of the Ten Commandments of God die in what is considered to be a mass murder and suicide, orchestrated by leaders of the cult.
- 2008 – Governor of New York Eliot Spitzer resigns after a scandal involving a high-end prostitute. Lieutenant Governor David Paterson becomes New York State governor.