1203

Events 
 April 16 – Philip II of France enters Rouen, leading to the eventual unification of Normandy and France.
 April 8 – Congress in Bilino Polje, where Ban Kulin officially declared his allegiance to the Roman Catholic Church and denounced the heresy.
 June 23 – Fleet of the Fourth Crusade enters Bosphorus.
 July 17 – Fourth Crusade captures Constantinople by assault; the Byzantine emperor Alexius III flees from his capital into exile.
 August 1 – Fourth Crusade elevates Alexius IV as Byzantine emperor, after the citizens of Constantinople proclaim as emperor Isaac II Angelus (Alexius IV's father).
 Unknown - John, Duke of Normandy gives the Ecrehos to the Abbey of Val-Richer.

 Heads of states 
 France – Philippe II, Auguste King of France (reigned from 1180 to 1223)