|Covid-19|January – Four-year-old Guttorm is proclaimed King of Norway; his "reign" ends with his death a few months later.
January 28 – Byzantine emperor Alexios IV Angelos is overthrown in a revolution.
February 5 – Alexios V Doukas is proclaimed Byzantine emperor.
April 13 – Fourth Crusade: The Crusaders take Constantinople by storm, and pillage the city for 3 days. Forces of the Republic of Venice seize the antique statues that will become the horses of Saint Mark.
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 Laskaris 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 I, Marquess 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.
Tsar Kaloyan is recognized as king of Bulgaria by Pope Innocent III after the creation of the Bulgarian Uniate church.
Valdemar II of Denmark, is recognized as king in Norway.
Angers and Normandy are captured by Philip II of France.
The Cistercian convent of Port-Royal-des-Champs is established.
The district of Cham becomes subject to Bavaria.
Hermann I, Landgrave of Thuringia submits to Philip of Swabia.
Beaulieu Abbey is founded.
The Channel Islands of Guernsey and Jersey decide, after a plebiscite of wealthy land owners, to remain with the English crown after Normandy is recaptured by Philip II of France.
Haakon IV of Norway (d. 1263)
Henry Raspe, Landgrave of Thuringia (d. 1247)
Abû 'Uthmân Sa'îd ibn Hakam al Qurashi, Ra'îs of Manûrqa (d. 1282)
Alice of Schaerbeek (d. 1250)
January 1 – King Haakon III of Norway
January – Isaac II Angelos, Byzantine emperor
February 8 – Alexios IV Angelos, Byzantine emperor
April 1 – Eleanor of Aquitaine, queen of France and England
August 11 – King Guttorm of Norway
August 14 – Minamoto no Yoriie, Japanese shogun (b. 1182)
September 30 or November 30 – Emeric, King of Hungary (b. 1174)
October 21 – Robert de Beaumont, 4th Earl of Leicester, English nobleman
November –Ban Kulin, ruler of Bosnia (b. 1163)
December 12 (or December 13) – Maimonides, Spanish rabbi and philosopher (b. 1135)
date unknown – Suleiman II of Rum
probable – Amalric of Bena, French theologian
Year 1204 (MCCIV) was a leap year starting on Thursday (link will display the full calendar) of the Julian calendar.