Year 1331 (MCCCXXXI) was a common year starting on Tuesday of the Julian calendar.

• September 8 – Stefan Dušan declares himself king of Serbia.
• September 27 – Battle of Płowce: The German Teutonic Knights and the Poles battle to a draw.

• The Sieges of Cividale del Friuli and Alicante begin.^[1]
• The Genkō War begins in Japan.
• Ibn Battuta visits Kilwa.
• The first recorded outbreak of the Black Death occurs, in the Chinese province of Hubei.

• February 16 – Coluccio Salutati, Florentine political leader (d. 1406)
• April 14 – Jeanne-Marie de Maille, French Roman Catholic saint (b. 1414)
• April 30 – Gaston III, Count of Foix (d. 1391)
• October 4 – James Butler, 2nd Earl of Ormonde (d. 1382)
• date unknown
  • Hamidüddin Aksarayî, Ottoman teacher of Islam (d. 1412)
  • Blanche d'Évreux, queen consort of France (d. 1398)
  • Michael Palaiologos, Byzantine prince
• probable – Salvestro de' Medici, provost of Florence (d. 1388)

• January 14 – Odoric of Pordenone, Italian explorer
• April 17 – Robert de Vere, 6th Earl of Oxford (b. c. 1257)
• May 12 – Engelbert of Admont, abbot of Admont in Styria
• October 27 – Abulfeda, Kurdish Syrian historian and geographer (b. 1273)
• November 11 – Stefan Uroš III Dečanski of Serbia (b. c. 1285)
• December 26 – Philip I, Prince of Taranto, titular Latin Emperor (b. 1278)
• December 30 – Bernard Gui, French inquisitor (b. 1261 or 1262)
• date unknown – Matilda of Hainaut, Princess of Achaea (b. 1293)