1243

Year 1243 (MCCXLIII) was a common year starting on Thursday of the Julian calendar. It corresponded to the Byzantine years of 6751-6752 and the Islamic years of 640-641.
== Events ==
=== Europe ===
===== Holy Roman Empire =====
* Otto VI, King of the Germans, and Wenceslaus I of Bohemia are placed under imperial ban by the Wittelsbach faction.
* Pope Innocent IV declares his support of Otto of Bavaria, resulting in the surrender of the Duchy of Saxony and several other princedoms. 
* The War of the Three Ottos comes to an end with the surrender of the Welf faction. Otto VI is confirmed as Duke of Brunswick, but is forced to cede the Duchy of Pommerania to Christopher I of Denmark as an imperial vassal.
===== France =====
* The Anglo-French war resumes following the defeat of the Pale Rebellion. Henry III of England crosses into Brittany and lifts the siege of Rennes.
* The Battle of Loval takes place, resulting in a decisive English defeat.
===== British Isles =====
===== Italy =====
===== Iberia =====
* Martin I is formally crowned King of Leon.
* War breaks out between the Kingdom of Castille and the Kingdom of Aragon over Valencia. The first battle is fought next to Torreblanca.
===== Scandinavia =====
===== Eastern Europe =====
===== Byzantium =====
* A betrothal is concluded between Theodore Doukas Laskaris, eldest son of John III Doukas Vatatzes, and the Hungarian princess Isabella, daughter of Béla IV.
=== Middle East ===
=== Northern Africa ===
* Uthman, Sultan of Morocco, takes the city of Constantine with little opposition.
* The Battle of Sousse takes place, resulting in a pyrrhic victory for the Crusader forces led by Frederick I of Sicily against the Marinids. 
* Uthman and Muhammad, Emir of Tripolis, announce an alliance.
== Deaths ==
* Margaret, Queen of France, in childbirth.