1340 CE
July – Trapezuntine Civil War: An abortive uprising occurs against Irene Palaiologina of Trebizond, the first of a number of coups, revolts, and succession disputes. Hundred Years' War: Battle of Sluys – The English fleet, under the command of Edward III of England, battles the French fleet, under that of Admiral Hugues Quiéret and treasurer Nicolas Béhuchet, assisted by Genoese mercenary galleys under Egidio Bocanegra, on the Low Countries coast. The French fleet is virtually destroyed, and both of its commanders are killed. Battle of Río Salado in Spain: The kings of Castile and Portugal defeat the Nasrid ruler of Granada and his Moroccan allies.
Geopolitics & Diplomacy
Conflict & Security
- April–July – Trapezuntine Civil War: An abortive uprising occurs against Irene Palaiologina of Trebizond, the first of a number of coups, revolts, and succession disputes.source
- June 24 – Hundred Years' War: Battle of Sluys – The English fleet, under the command of Edward III of England, battles the French fleet, under that of Admiral Hugues Quiéret and treasurer Nicolas Béhuchet, assisted by Genoese mercenary galleys under Egidio Bocanegra, on the Low Countries coast. The French fleet is virtually destroyed, and both of its commanders are killed.source
- July 26 – Hundred Years' War – Battle of Saint-Omer: The French defeat the English.source
- September 25 – Hundred Years' War: The temporary Truce of Espléchin is signed between England and France.source
- October 30 – Battle of Río Salado in Spain: The kings of Castile and Portugal defeat the Nasrid ruler of Granada and his Moroccan allies.source
Exploration & Expansion
Health & Medicine
Culture & Society
Births
- March 5 – Cansignorio della Scala, Lord of Verona (d. 1375)source
- March 6 – John of Gaunt, 1st Duke of Lancaster (d. 1399)source
- August – Haakon VI, king of Norway 1355–1380 and of Sweden 1362–1364 (d. 1380)source
- October – Geert Groote, Dutch founder of the Brethren of the Common Life (d. 1384)source
- November 30 – John, Duke of Berry, son of John II of France (d. 1416)source
- John of Nepomuk, saint of Bohemia (d. 1393)source
- Narayana Pandit, Indian mathematician (d. 1400)source
- Margaret Drummond, queen consort of Scotland (d. 1375)source
- Philip van Artevelde, Flemish patriot (d. 1382)source
- Enguerrand VII, Lord of Coucy (d. 1397)source
Deaths
- March 31 – Ivan I of Moscow (b. 1288)source
- April 5 – William Melton, English archbishopsource
- April 6 – Emperor Basil Megas Komnenos of Trebizondsource
- April 7 – Bolesław Jerzy II of Mazovia (b. 1308)source
- December 2 – Geoffrey le Scrope, Chief Justice of King Edward III of Englandsource
- December 4 – Henry Burghersh, English bishop and chancellor (b. 1292)source
- December 20 – John I, Duke of Bavaria (b. 1329)source
- date unknown – Simonida, queen consort of Serbia (b. 1294)source
- date unknown – Friedrich von Pernstein, Archbishop of Rigasource