Why was the square named Trafalgar Square?

The square was originally called Charing Cross and derived its name from the Eleanor cross, erected on the spot by King Edward I in 1290 to commemorate the last resting-place of the body of his queen Eleanor of Castile, as it was brought to Westminster for burial. Over 200 years later, Henry VIII replaced the Eleanor cross with a grander cross designed by Hans Holbein the Younger.

On 25 March 1815, the Duke of Wellington defeated Napoleon's army at the Battle of Waterloo. In early 1820, King George IV approved the development of a formal square as a war memorial to commemorate British victories in the Napoleonic wars, particularly those of Lord Nelson at Cape Trafalgar. The square originally had a statue of George IV, but this was so poorly received that the statue was eventually replaced by a statue of Lord Nelson. It is because of this statue that the square became known as Trafalgar Square.