Events of 1400

• January – Henry IV quells the Epiphany Rising and executes the Earls of Kent, Huntingdon and Salisbury and the Baron le Despencer for their attempt to have Richard II of England restored as King.
  • 14 February – Richard II of England dies by means unknown in Pontefract Castle. It is likely that King Henry IV ordered the death of Richard by starvation to prevent further uprisings.
  • August – The princes of the German states vote to depose Wenceslaus as Holy Roman Emperor due to his weak leadership and his mental illnesses.
    • 21 August – Rupert, Count Palatine of the Rhine, is elected as Holy Roman Emperor.
• September 16 – Owain Glyndŵr is proclaimed Prince of Wales by his followers and begins attacking English strongholds in north-east Wales.
• December – Manuel II Palaiologos becomes the first (and last) Byzantine Emperor to visit England.
• Frederick, Duke of Brunswick-Lüneburg is declared as a rival to Holy Roman Emperor Wenceslaus. However, Frederick is murdered shortly after.
• Timur defeats both the Ottoman Empire and the Mamluk Sultanate of Egypt to capture the city of Damascus in present-day Syria. Much of the city's inhabitants are subsequently massacred by Timur's troops.
• Timur conquers the Empire of The Black Sheep Turkomans, in present-day Armenia, and the Jalayirid Dynasty in present-day Iraq. Black Sheep ruler Qara Yusuf and Jalayirid Sultan Ahmad flee and take refuge with the Ottoman Sultan Bayezid I.
• Scotland resists an English invasion led by Henry 'Hotspur' Percy.
• Newcastle-upon-Tyne created County Corporate by Henry IV.
• In present-day Korea, King Jeongjong of Joseon abdicates in fear of an attack by his ambitious younger brother, Taejong. Taejong succeeds to the throne.
• Prince Parameswara establishes the Malacca Sultanate in present-day western Malaysia and northern Sumatra.
• Five year old Tran An is forced to abdicate as ruler of Dai Viet (now Vietnam) in favour of his maternal grandfather Ho Quy Ly, ending the Tran Dynasty and starting the Hồ Dynasty. Ho Quy Ly subsequently changes the country's name to Dai Ngu.
• Hananchi succeeds Min as King of Hokuzan in present-day north Okinawa, Japan.
• Wallachia (now southern Romania) resists an invasion by the Ottomans.
• Jean Froissart completes his Chronicles detailing the events of the 14th Century in France.
• The Medici family becomes powerful in Florence.
• Europe is reported to have around 52 million inhabitants.
• The Kingdom of Kongo begins.

Births

• January 13 – Infante John of Portugal, the Constable (d. 1442)
• December 25 – John Sutton, 1st Baron Dudley, Lord Lieutenant of Ireland (d. 1487)
• date unknown
  • James Touchet, 5th Baron Audley (d. 1459)
  • Luca della Robbia, Florentine sculptor (d. 1482)
  • Isabella, Duchess of Lorraine (d. 1453).
  • Richard Neville, 5th Earl of Salisbury, English politician (d. 1460)
  • Owen Tudor, Welsh courtier (d. 1461)
  • Rogier van der Weyden (other date is 1399)

Deaths

• January 5
  • John Montacute, 3rd Earl of Salisbury, English politician (executed)
  • Thomas Holland, 1st Duke of Surrey, English politician (executed) (b. 1374)
• January 13 – Thomas le Despenser, 1st Earl of Gloucester, English politician (executed)
• January 16 – John Holland, 1st Duke of Exeter, English politician (executed)
• February 14 – King Richard II of England (probably murdered) (b. 1367)
• April 28 – Baldus de Ubaldis, Italian jurist (b. 1327)
• 5 June – Frederick, Duke of Brunswick-Lüneburg, rival Holy Roman Emperor
• October 25 – Geoffrey Chaucer, English poet
• date unknown – Narayana Pandit, Indian mathematician (b. 1340)