Events of 1403

• February 7 - King Henry IV of England marries Joanna of Navarre, the daughter of Charles d'Evreux, King of Navarre.
• March 12 - As King Martin I of Aragon helps to end the siege by the French of the papal palace in Avignon, Antipope Benedict XIII flees to Aragon.
• April - Balša III succeeds his father Đurađ II as ruler of the Principality of Zeta (now the Republic of Montenegro).
• Harry "Hotspur" Percy forms an alliance with Welsh rebel Owain Glyndŵr.
• July 21 - Battle of Shrewsbury: King Henry IV of England defeats a rebel army led by "Hotspur" Percy, who is killed in the battle by an arrow in his face.

  Undated

• Jan Hus begins preaching Wycliffite ideas in Bohemia.
• Ming Emperor Yongle moves the capital of China from Nanjing to Beijing.
• The Gur-e Amir Mausoleum is built by Timur after the death of his grandson Muhammad-Sultan, and eventually becomes the family mausoleum of the Timurid dynasty.
• While the Ottomans are at civil war, the Byzantine Empire reclaims the European coast of the Sea of Marmara and Thessalonica. The emperor's son Andronikos Palaiologos is given the title of Lord of Thessalonike.
• The world's first quarantine station is built in Venice to quarantine against the Black Death.
• Battle of Modon: - the French under Jean Le Maingre defeat the Venetians.
• Grand Duke Vytautas ends his alliance with Muscovy and captures Vyazma and Smolensk.
• The Yongle Encyclopedia (then one of the world's earliest and largest known general encyclopedias) is commissioned by the Chinese Ming Dynasty emperor Yongle.
• Stefan Lazarević establishes Belgrade as the capital of the Serbian Despotate.
• The Worshipful Company of Stationers and Newspaper Makers (better known as the Stationers' Company) is founded in England (currently one of the Livery Companies of the City of London).
• Georgia makes peace with Timur but has to recognise him as a suzerain and pay him tribute.
• Tadgh Ruadh mac Maelsechlainn O Cellaigh succeeds Conchobar an Abaidh mac Maelsechlainn O Cellaigh as King of Hy-Many in present-day County Galway and County Roscommon in Ireland.
• Maolmhordha mac Con Connacht succeeds Giolla Iosa mac Pilib as King of East Breifne, in present-day County Leitrim and County Cavan, Ireland.
• The Temple of a City God is constructed in Shanghai, China.
• Ruy Gonzalez de Clavijo, an ambassador from the king of Castile, arrives in Samarkand.
• Yongle orders his coastal provinces to build a vast fleet of ships, with construction centered at Longjiang near Nanjing; the inland provinces are to provide wood and float it down the Yangzi River.
• probable - Ououso becomes King of Nanzan in present-day south Okinawa, Japan.

Ongoing