1203
1203 (MCCIII) was .
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)