Events

• February - Byzantine emperor Alexius IV is overthrown in a revolution, and Alexius V is proclaimed emperor.
• April 12 - The Fourth Crusade take Constantinople by storm, and pillage the city for three days. End of the Fourth Crusade.
• May 16 - Baldwin, Count of Flanders is crowned emperor of the Latin Empire a week after his election by the members of the Fourth Crusade.
• As a result of the fall of Constantinople and the creation of the Latin Empire, Bulgaria is forced to cede Macedonia to the new state.
• Theodore I Lascaris flees to Nicaea after the capture of Constantinople, and establishes the Empire of Nicaea; Byzantine successor states are also established in Epirus and Trebizond.
• Boniface of Montferrat, a leader of the Fourth Crusade, founds the Kingdom of Thessalonica.
• The writings of French theologian Amalric of Bena are condemned by the University of Paris and Pope Innocent III.
• Valdemar II, King of Denmark, is recognized as king in Norway.
• Angers and Normandy are recaptured from England by Philip II of France.
• The Cistercian convent of Port-Royal is established.
• The district of Cham becomes subject to Bavaria.
• Philip of Swabia becomes a subject of Hermann I of Thuringia.

Births

• Haakon IV, King of Norway
• Heinrich Raspe, Landgraf of Thuringia

Deaths

• February - Byzantine emperor Isaac II Angelus
• March 31 - Eleanor of Aquitaine, queen of France and England (b. 1121)
• December 13 - Maimonides, Jewish philosopher
• Minamoto no Yoriie, second shogun of the Kamakura Shogunate of Japan
• Amalric of Bena, French theologian

Heads of states

• England - John I King of England (reigned from 1199 to 1216)
• France - Philippe II, Auguste King of France (reigned from 1180 to 1223)