- 1525 The Swiss Anabaptist Movement is born when Conrad Grebel, Felix Manz, George Blaurock, and about a dozen others baptize each other in the home of Manz's mother in Zürich, breaking a thousand-year tradition of church-state union.
- 1793 Louis XVI of France is executed by the guillotine in Paris, following his conviction for high treason.
- 1968 The Battle of Khe Sanh - one of the most publicized and controversial battles of the Vietnam War - begins at the Khe Sanh Air Base.
- 2008 Black Monday in worldwide stock markets. FTSE 100 had its biggest ever one-day points fall, European stocks closed with their worst result since 9/11, and Asian stocks drop as much as 15%.
USS Nautilus, the first nuclear-powered submarine, launched on the Thames River in Connecticut
On January 21, 1954