||Wikimedia Commons has media related to 1391.
Year 1391 (MCCCXCI) was a common year starting on Sunday (link will display full calendar) of the Julian calendar.
- Manuel II Palaiologos becomes Byzantine emperor after his father, John V Palaiologos, dies of a nervous breakdown, due to his continued humiliation by the Ottoman Empire.
- Yusuf II succeeds Muhammed V, as Nasrid Sultan of Granada (now southern Spain).
- Stephen Dabiša succeeds Stephen Tvrtko I, as King of Bosnia.
- Shah Mansur becomes leader of the Timurid-occupied Muzaffarid Empire, in central Persia.
- A group of Muzaffarids under Zafar Khan Muzaffar establish a new Sultanate at Gujarat, in western India.
- Vytautas the Great, claimant to the throne of Lithuania, forms an alliance with Muscovy.
- Roman I succeeds Petru II, as Prince of Moldavia (now Moldova and north-eastern Romania).
- Konrad von Wallenrode succeeds Konrad Zöllner von Rotenstein, as Grand Master of the Teutonic Knights.
- Bridget of Sweden is canonized by Pope Boniface IX.
- Ushkuinik pirates from Novgorod sack the Muscovy towns of Zhukotin and Kazan.
- The Chinese invent toilet paper for use by their emperors.
- Henry I Sinclair, Earl of Orkney, takes control of the Shetland Islands and the Faroe Islands.
- The University of Ferrara is founded on the Italian Peninsula.
- The Ming government orders 50 million trees planted in the Nanjing area.