Year 1252 (MCCLII) was a leap year starting on Monday (link will display the full calendar) of the Julian calendar.
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.
December 25 – Christopher I of Denmark is crowned King of Denmark in the Lund Cathedral.
The first European gold coins are minted in the Italian city of Florence, and are known as florins.
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 Swedish city of Stockholm is founded by Birger Jarl.
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 masters degree.
In astronomy, work begins on the recording of the Alfonsine tables.
The classic Japanese text Jikkunsho is completed.
The Chinese era Chunyou ends.
The Mongols take the westernmost province of the Song dynasty empire.
March 25 – Conradin, Duke of Swabia (d. 1268)
Safi-ad-din Ardabili, Persian Sufi leader
Eleanor de Montfort, princess of Wales (d. 1282)
January – Bohemond V, Prince of Antioch
January 23 – Isabella, Queen of Armenia
February 3 – Sviatoslav III of Vladimir, Prince of Novgorod (b. 1196)
April 6 – Saint Peter of Verona
May 3 or May 4 – Günther von Wüllersleben, Grand Master of the Teutonic Knights
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
Saint Zdislava Berka
Kujō Michiie, Japanese regent
Catherine of Ymseborg, Swedish queen consort
Yesu Mongke, Khan of the Chagatai Khanate
1252 Wikipedia (Text) CC BY-SA