March 18 is the 78th day of the year. There are 288 days remaining until the end of the year.
- 1314 – Jacques de Molay, the 23rd and last Grand Master of the Knights Tempar, was burned at the stake.
- 1634 – Marie-Madeleine Pioche de la Vergne, French author of first historical novel, was born. She died in 1693.
- 1673 – John Berkeley, 1st Baron Berkeley of Stratton sold his part of New Jersey to the Religious Society of Friends, known as Quakers.
- 1766 – The British Parliament repealed the Stamp Act.
- 1834 – Six farm laborers from Tolpuddle, England were sentenced to be transported to Australia for forming a trade union.
- 1850 – American Express was founded by Henry Wells and William Fargo.
- 1874 – Hawaii signed a treaty with the US granting exclusive trading rights.
- 1922 – In India, Mohandas Gandhi was sentenced to six years in prison for civil disobedience.
- 1925 – A tornado hit Missouri, Illinois, and Indiana, killing 695 people.
- 1942 – The War Relocation Authority was established in the United States to take Japanese Americans into custody.
- 1965 – Cosmonaut Aleksei Leonov left his spacecraft for 12 minutes, becoming the first person to walk in space.
- 1968 – The U.S. Congress repealed the requirement for a gold reserve to back United States currency.
- 1989 – In Egypt, a 4,400-year-old mummy was found near the Pyramid of Cheops.
- 1990 – The largest art theft in United States history: 12 paintings worth $300 million were stolen from a museum in Boston, Massachusetts.
- 1992 – White South Africans vote overwhelmingly in favor to end the racist policy of Apartheid.
- 2003 – British Sign Language was recognized as an official British language.