1217

By area

Asia

• Mukhali returns to Genghis Khan's camp in Mongolia, and receives the hereditary title of prince, a golden seal, and a white standard with nine tails and a black crescent in the middle. He is appointed commander in chief of operations in North China.
• The Fifth Crusade reaches the Holy Land.

  Europe

• April 9 - Peter II of Courtenay is crowned emperor of the Latin Empire of Constantinople at Rome, by Pope Honorius III.
• May 20 - First Barons' War in England: Occupying French forces are defeated at the Battle of Lincoln, by English royal troops led by William Marshal, Earl of Pembroke, and survivors are forced to flee south.
• June 6 - King Henry I of Castile dies aged 13, from the fall of a roof tile in Palencia, an event which his regent, Álvaro Núñez de Lara, attempts to conceal. Henry's sister Berengaria succeeds to the throne.
• June - Haakon Haakonsson becomes King Haakon IV of Norway, following the death of Inge II, and largely ends the civil war era in Norway, reigning until 1263.
• August 24 - First Barons' War: In the Battle of Sandwich in the English Channel, English forces destroy the French, and the French mercenary Eustace the Monk is captured and beheaded.
• August 31 - Ferdinand becomes King of Castile, upon the abdication of his mother Berengaria.
• September 12 - The First Barons' War in England is ended by the Treaty of Kingston upon Thames; The French and Scots are to leave England, and an amnesty is granted to rebels.
• September 20 - The Treaty of Lambeth is signed, ratifying the Treaty of Kingston.
• September 21 - Livonian Crusade: The Livonian Brothers of the Sword and allied Livs and Letts defeat the Estonian army in the Battle of St. Matthew's Day, and kill their leader Lembitu.
• October 18 - Fifth Crusade, Reconquista: Alcácer do Sal is reconquered by the troops of King Afonso II of Portugal.
• November - In the Kingdom of Castile, former regent Álvaro Núñez de Lara is captured, and forced to relinquish all his castles.
• Stefan Nemanjić is elevated to be the first King of the Serbian lands by Pope Honorius III, and crowned by Stefan's brother, Archimandrite Sava, in Žiča.
• A decree made in England establishes that only Englishmen can be clergy of Ireland.