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Year 1402 (MCDII) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar.
- The Malacca Sultanate is established at Melaka Darul Azim (now known as Melaka Darul Azim, Malaysia).
- January 29 – King Jogaila of the Poland–Lithuania Union answers the rumblings against his rule of Poland, by marrying Anna of Celje, a granddaughter of Casimir III of Poland.
- March 26 – David Stewart, Duke of Rothesay, heir to the throne of Scotland, dies while being held captive by his uncle, Robert Stewart, 1st Duke of Albany.
- May 21 – Following the death of Queen Maria of Sicily, her husband Martin I of Sicily, now sole ruler, marries Blanche of Navarre.
- June 22
- June 26 – Battle of Casalecchio: Gian Galeazzo Visconti, the Duke of Milan, crushes the forces of Bologna and Florence, but he dies from a fever later this year, and is succeeded by his son, Gian Maria Visconti.
- July 12 – The Ming Dynasty prince Zhu Di and his army occupies the Ming capital, Nanjing. The Jianwen Emperor is either lost or killed, and Zhu Di takes over the throne as the Yongle Emperor (this marks the end of the Jingnan Campaign).
- July 20 – Battle of Ankara: An invading Timurid Dynasty force defeats the Ottoman Sultan Bayezid I, who is captured. A period of interregnum begins in the Ottoman Empire, with the future Mehmed I as one of the leading claimants to the throne. After Serbia is freed from Ottoman rule, Stefan Lazarević is crowned Despot of Serbia.
- September – Penal Laws against Wales The English Parliament passes the Penal Laws against Wales. The Laws stop the Welsh from gathering together, obtaining office, carrying arms and living in English towns. Any Englishman who marries a Welsh woman also comes under the laws.
- September 14 – Battle of Homildon Hill: Northern English nobles, led by Sir Henry "Hotspur" Percy, and using longbows, decisively defeat a Scottish raiding army and capture their leader, the Earl of Douglas.
Capture of Bayezid I after Battle of Ankara
- After the Christian Knights of Saint John, who are ruling Smyrna, refuse to convert to Islam or pay tribute, Timur has the entire population massacred. The Knights of Saint John subsequently begin building Bodrum Castle in Bodrum, to defend against future attacks.
- Conquest of the Canary Islands: King Henry III of Castile sends French explorer Jean de Béthencourt to colonize the Canary Islands. Béthencourt receives the title King of the Canary Islands, but recognizes Henry as his overlord. This marks the beginning of the Spanish Empire.
- The Genoese regain control of Monaco.
- The White Sheep Turkmen Empire, in present-day northern Iraq and Iran, moves its capital from Amida to Diyarbakır.
- Moldavia becomes a vassal of Poland, in order to protect itself from an invasion by Hungary.
- Maria II Zaccaria succeeds her husband, Peter of Saint Superan, as ruler of the Principality of Achaea (now southern Greece).
- Conchobar an Abaidh mac Maelsechlainn O Cellaigh succeeds Maelsechlainn mac William Buidhe O Cellaigh, as King of Uí Maine in present-day County Galway and County Roscommon, in Ireland.
- The University of Würzburg is founded.
- The Kangnido map of the world is completed in Joseon Dynasty Korea.
- The Great Comet of 1402 is sighted.
- A big fire in the city of Utrecht starts near the Jacobus Church.
- February 6 – Louis I, Landgrave of Hesse, Landgrave of Hesse (1413-1458) (d. 1458)
- April 28 – Nezahualcoyotl, Acolhuan philosopher, warrior, poet and ruler (d. 1472)
- May 2 – Eleanor of Aragon, Queen of Portugal (d. 1445)
- June 7 – Ichijō Kaneyoshi, Court noble (d. 1481)
- August 15 – Humphrey Stafford, 1st Duke of Buckingham (d. 1460)
- September 29 – Fernando, the Saint Prince, of Portugal (d. 1443)
- November 23 – Jean de Dunois, illegitimate son of Louis I (d. 1468)
- date unknown – Leonor of Aragon, Queen of Portugal (d. 1445)