From Infogalactic: the planetary knowledge core
|Centuries:||13th century – 14th century – 15th century|
|Decades:||1340s 1350s 1360s – 1370s – 1380s 1390s 1400s|
|Years:||1375 1376 1377 – 1378 – 1379 1380 1381|
|1378 by topic|
|State leaders - Sovereign states|
|Birth and death categories|
|Births - Deaths|
|Establishments and disestablishments categories|
|Establishments - Disestablishments|
|Art and literature|
|1378 in poetry|
|Ab urbe condita||2131|
|English Regnal year||1 Ric. 2 – 2 Ric. 2|
|Chinese calendar||丁巳年 (Fire Snake)
4074 or 4014
— to —
戊午年 (Earth Horse)
4075 or 4015
|- Vikram Samvat||1434–1435|
|- Shaka Samvat||1300–1301|
|- Kali Yuga||4479–4480|
|Japanese calendar||Eiwa 4
|Minguo calendar||534 before ROC
|Thai solar calendar||1920–1921|
|Wikimedia Commons has media related to 1378.|
- March – In England, John Wycliffe tries to promote his ideas for Catholic reform by laying his theses before parliament and making them public in a tract. He is subsequently summoned before Archbishop of Canterbury, Simon of Sudbury, at the episcopal palace at Lambeth to defend his actions.
- April 9 – Following the death of Pope Gregory XI and riots in Rome calling for a Roman pope, the cardinals, who are mostly French, elect Pope Urban VI (Bartolomeo Prignano, Archbishop of Bari) as the 202nd Pope.
- July – Revolt of the Ciompi – discontent wool carders briefly take over the government of Florence. For the first time, a European government represents all social classes.
- August 4 – Gian Galeazzo Visconti succeeds his father, Galeazzo II Visconti, as ruler of Milan.
- September – A contract is set up between Richard le Scrope, 1st Baron Scrope of Bolton and the mason Johan Lewyn for the construction of Bolton Castle.
- September 20 – Unhappy with Pope Urban's critical attitude towards them, the majority of the cardinals meet at Fondi and elect Clement VII as antipope and establish a rival papal court at Avignon. This split within the Catholic Church becomes known as the Western Schism.
- November 10 – Estimated appearance date of Halley's Comet.
- November 29 – Charles IV, Holy Roman Emperor, dies in Prague. He is succeeded by his son, Wenceslaus as King of Bohemia but the office of Holy Roman Emperor falls into abeyance until Charles's son Sigismund is crowned in 1433.
- Holy Roman Emperor Charles IV visits his nephew Charles V of France to publicly celebrate the friendship between their two nations.
- France, Aragon, Castile and León, Cyprus, Burgundy, Savoy, Naples and Scotland choose to recognise Antipope Clement VII. Denmark, England, Flanders, the Holy Roman Empire, Hungary, northern Italy, Ireland, Norway, Poland and Sweden continue to recognise Pope Urban VI.
- Dmitri Donskoi of Moscow & Vladimir resists a small invasion by the Mongol Blue Horde.
- Tokhtamysh dethrones Timur Malik as Khan of the White Horde.
- Kara Osman establishes the Turkomans of the White Sheep dynasty at Diyarbakır in present-day southeast Turkey.
- The Turks capture the town of Ihtiman in west Bulgaria.
- Uskhal Khan succeeds his father, Biligtü Khan, as ruler of the Yuan Dynasty in Mongolia.
- Balša II succeeds his father, Durađ I, as ruler of Zeta (now Montenegro).
- Tai Bian succeeds Zhao Bing Fa as King of Mong Mao (now northern Myanmar).
- Da'ud Shah succeeds his assassinated nephew, Aladdin Mujahid Shah, as Bahmani Sultan in present-day southern India. Da'ud Shah is assassinated in the same year and is succeeded by Mohammed Shah II.
- Sa'im al-Dahr is hanged for blowing the nose off the Sphinx.
- January 23 – Louis III, Elector Palatine (d. 1436)
- May 27 – Zhu Quan, Chinese military commander, historian and playwright (d. 1448)
- August 16 – Hongxi Emperor of China (d. 1425)
- October 24 – David Stewart, Duke of Rothesay (d. 1402)
- December 31 – Pope Callixtus III (d. 1458)
- date unknown
- February 6 – Jeanne de Bourbon, queen of Charles V of France (b. 1338)
- March 27 – Pope Gregory XI
- July – Owain Lawgoch, titular Prince of Wales – assassinated (b. c. 1330)
- August 4 – Galeazzo II Visconti, Lord of Milan (b. c. 1320)
- August 16 – San Rocco di Venezia, patron saint of pestilence (b. 1340)
- November 29 – Charles IV, Holy Roman Emperor (b. 1316)