|Ab urbe condita||2006|
|Balinese saka calendar||1174–1175|
|English Regnal year||37 Hen. 3 – 38 Hen. 3|
|Chinese calendar||壬子年 (Water Rat)|
3949 or 3889
— to —
癸丑年 (Water Ox)
3950 or 3890
|- Vikram Samvat||1309–1310|
|- Shaka Samvat||1174–1175|
|- Kali Yuga||4353–4354|
|Japanese calendar||Kenchō 5|
|Minguo calendar||659 before ROC|
|Thai solar calendar||1795–1796|
1379 or 998 or 226
— to —
1380 or 999 or 227
- January 18 – Henry I of Cyprus dies, and is succeeded as king by his newborn son, Hugh II.
- July 4 – William II, Count of Holland, defeats the Flemish army at Westkapelle.
- July 6 – Mindaugas is crowned as the only King of Lithuania.
- August 6 – King Henry III of England leads an expedition to Gascony, to repel a rumoured invasion from Castile. Simon de Montfort, 6th Earl of Leicester, returns from Gascony to England where he allies himself with barons who oppose Henry.
- August 9 – Papal bull Solet annuere extablishes the rule of Clare of Assisi over the Poor Clares two days before her death.
- October – Pope Innocent IV returns to Rome, having left nine years earlier in 1244 to depose Frederick II, Holy Roman Emperor, and being unable to return until after Frederick's death, due to the agitation throughout Europe caused by that action.
- Having rebuffed the armed forces of Conrad IV of Germany, Pope Innocent IV offers Sicily to Edmund, son of King Henry III of England.
- A series of naval wars begins between the Italian city-states of Genoa and Venice, which will continue sporadically until 1371.
- Henry III of England meets with English nobles and church leaders to reaffirm the validity of Magna Carta.
- Halych–Volynia becomes a vassal state to the expanding Mongol Empire.
- Matthew Paris completes the major part of his Chronica Majora, a chronicle of English history.
- The upper Basilica of Saint Francis of Assisi, the earliest important structure of Italian Gothic architecture, is completed in Assisi, Italy.
- Sligo Abbey is built in Sligo, Ireland.
- The Domus Conversorum, a building and institution in London for Jews who had converted to Christianity, is established by King Henry III of England.
- April 28 – Nichiren, a Japanese Buddhist monk, declares his intent to preach the Lotus Sutra and Namu Myōhō Renge Kyō as the true Buddhism, thus founding Nichiren Buddhism.
- May – King Louis IX of France dispatches William of Rubruck from Constantinople, on a missionary journey to convert the Tatars of central and eastern Asia. Later that year, William records the first meeting between European Christians and Buddhists.
- Hulegu's advance guard attacks the Nizari strongholds in east of Persia.
- The Mongol Empire launches attacks on the Muslim cities of Baghdad and Cairo.
- The Mongol Empire destroys the Dali Kingdom in modern Yunnan and incorporates the region into their empire.
- Kublai Khan introduces the baisha xiyue song and dance suite to the music of Yunnan.
- The Chinese era Baoyou begins in the Southern Song dynasty of China.
- The Mongols defeat the Thai Confederacy.
- March 20 – Wareru or Wagaru, born Gadu, Burmese commoner who founded the Hanthawaddy Kingdom (Pegu) (d. 1307)
- October 17 – Ivo of Kermartin, Breton canon lawyer, priest and saint (d. 1303)
- date unknown
- November 25 – Katherine of England, daughter of Henry III of England
- January 18 – King Henry I of Cyprus (b. 1217)
- April 3 – Richard of Chichester, English bishop and saint (b. 1197)
- June 11 – Amadeus IV, Count of Savoy (b. 1197)
- July 8 – Theobald I of Navarre (b. 1201)
- August 11 – Clare of Assisi, Italian saint, follower of Francis of Assisi (b. 1194)
- September 22 – Dōgen, Japanese founder of the Soto school of Zen Buddhism (b. 1200)
- September 23 – Wenceslaus I of Bohemia, king of Bohemia (b. c.1205)
- October 9 – Robert Grosseteste, English bishop, statesman and theologian (b. c. 1175)