1231

Events

* April 9 — After a bizarre weather phenomena of yellowish clouds and dust chokes the air around Hangzhou, Song Dynasty, China, obscuring the sky and sun, a fire breaks out at night in the southeast of the city, which continues into the next day. Fighting the flames is difficult due to limited visibility. When the fires are extinguished, it is discovered that an entire district of some 10,000 houses in the southeast of the city were consumed by the flames.
* Ardengus becomes bishop of Florence.
* Emperor Frederick II promulgates the Constitutions of Melfi (also known as "Liber Augustalis"), a collection of laws for Sicily.
* Llywelyn the Great launches a campaign against the Norman lordships in Wales.
* Mongol troops cross the Yalu River into Korea, then under the Goryeo Kingdom.
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Births

* March 17 - Emperor Shijō of Japan (d. 1242)
* Guo Shoujing, Chinese astronomer and mathematician
* John de Warenne, 7th Earl of Surrey (d. 1304)
* Roger Mortimer, 1st Baron Wigmore (d. 1282)

Deaths

* April 6 - William Marshal, 2nd Earl of Pembroke
* June 13 - Anthony of Padua, Portuguese saint (b. 1195)
* November 6 - Emperor Tsuchimikado of Japan (b. 1196)
* November 17 - Saint Elisabeth of Hungary, daughter of Andrew II of Hungary (b. 1207)
* Abd-el-latif, Arab physician and traveller