Year 1252 (MCCLII) was a leap year starting on Monday of the Julian calendar.
Events
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By place
Europe
- April 6 – Saint Peter of Verona is assassinated by Carino of Balsamo.
- May 15 – Pope Innocent IV issues the papal bull Ad exstirpanda, which authorizes the torture of heretics in the Medieval Inquisition. Torture quickly gains widespread usage across Catholic Europe.
- June 1 – Alfonso X is proclaimed king of Castile and León.
- July – The settlement of Stockholm in Sweden is founded, by Birger Jarl.
- December 25 – Christopher I of Denmark is crowned King of Denmark, in the Lund Cathedral.
- The Polish land of Lebus is incorporated into the German state of Brandenburg, marking the start of Brandenburg's expansion into previously Polish areas (Neumark).
- The Lithuanian city of Klaipėda (Memel) is founded by the Teutonic Knights.
- The town and monastery of Orval Abbey in Belgium burn to the ground; rebuilding takes 100 years.
- Thomas Aquinas travels to the University of Paris, to begin his studies there for a master's degree.
- In astronomy, work begins on the recording of the Alfonsine tables.
Asia
- The classic Japanese text Jikkunsho is completed.
- The Chinese era Chunyou ends (→ Emperor Lizong).
- Mongol conquest of the Song dynasty: the Mongols take the westernmost province of the Song dynasty empire.</onlyinclude>
- New Mongol invasion of Tibet.
Births
- March 25 – Conradin, Duke of Swabia (d. 1268)
- Safi-ad-din Ardabili, Persian Sufi leader
- Eleanor de Montfort, Princess of Wales, English-born consort (d. 1282)
Deaths
- January 1 – Saint Zdislava Berka, Bohemian lay Dominican benefactress
- January 23 – Isabella, Queen of Armenia
- January – Bohemond V, Prince of Antioch
- February 3 – Sviatoslav III of Vladimir, Prince of Novgorod (b. 1196)
- April 1 – Kujō Michiie, Japanese regent
- April 6 – Saint Peter of Verona<!--ref name=":0" /-->
- May 30 – King Ferdinand III of Castile and Leon
- June 6 – Robert Passelewe, Bishop of Chichester
- June 9 – Otto I, Duke of Brunswick-Lüneburg
- June 29 – Abel, King of Denmark (b. 1218)
- August 1 – Giovanni da Pian del Carpine, Italian chronicler of the Mongol Empire
- November 27 – Blanche of Castile, queen of Louis VIII of France and regent of France (b. 1188)
- date unknown
- John of Basingstoke, English scholar and ecclesiastic
- Henry I, Count of Anhalt
- Sorghaghtani Beki, Mongolian empress and regent
- Catherine Sunesdotter, Swedish queen consort
- Yesü Möngke, Khan of the Chagatai Khanate