- 1096 21 Oct The People's Crusade, led by Peter the Hermit, is slaughtered by Seljuk Turks at the Battle of Civetot.
- 1805 21 Oct The Royal Navy defeats the Franco-Spanish fleet at the Battle of Trafalgar, but Nelson is killed.
- 1854 21 Oct Florence Nightingale leaves England with 38 nurses, to tend to the British wounded from the Crimean War.

