1204Centuries: 12th century - 13th century - 14th century
- 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.
- 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.
- February - Byzantine emperor Isaac II Angelus
- 1 April - Eleanor of Aquitaine
- Maimonides, Jewish philosopher
- Minamoto no Yoriie, second shogun of the Kamakura Shogunate of Japan
- Amalric of Bena, French theologian