Year 1387 (MCCCLXXXVII) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar.

• Elizabeta Kotromanic, mother of Mary, Queen of Hungary and the regent of Hungary, is murdered in prison by the Croatian rebels (her daughter is liberated on 4 June).

• January 1 – Charles III ascends to the throne of Navarre, after the death of his father, Charles II.^[1]
• January 5 – John I succeeds his father, Peter IV, as King of Aragon and Valencia, and forms an alliance with France and Castile.
• March 11 – Battle of Castagnaro: Padua, led by John Hawkwood, is victorious over Giovanni Ordelaffi of Verona.
• March 24–25 – Battle of Margate off the coast of Margate: The Kingdom of England is victorious over a Franco-Castilian-Flemish fleet.
• June 2 – John Holland, a maternal half-brother of Richard II of England, is created Earl of Huntingdon.
• August 22 – Olaf, King of Norway and Denmark and claimant to the throne of Sweden, dies. The vacant thrones come under the regency of his mother Margaret I of Denmark, who will soon become queen in her own right.
• September 27 – Petru of Moldavia pays homage to Władysław II Jagiełło, making Moldavia a Polish fief (which it will remain until 1497).
• December 19 – Battle of Radcot Bridge: Forces loyal to Richard II of England are defeated by a group of rebellious barons known as the Lords Appellant. Richard II is imprisoned, until he agrees to replace all the councillors in his court.

• Timur conquers the Muzaffarid Empire in central Persia, and appoints three puppet rulers.
• Khan Tokhtamysh of the Golden Horde invades the Timurid Empire, but has to withdraw soon after, due to heavy snow.
• Maghan II succeeds his brother, Musa II, as Mansa of the Mali Empire

• July 6 – Queen Blanche I of Navarre (d. 1441)
• date unknown – Henriette, Countess of Montbéliard, regent of Württemberg (d. 1444)

• January – Elizabeth of Bosnia, regent of Hungary
• January 1 – King Charles II of Navarre (b. 1332)^[2]
• January 6 – Peter IV of Aragon (b. 1319)
• July 20 – Robert IV of Artois, Count of Eu (poisoned) (b. 1356)
• July 22 – Frans Ackerman, Flemish statesman (b. 1330)
• August 23 – King Olaf IV of Norway/Olaf II of Denmark (b. 1370)
• date unknown
  • Richard Óg Burke, second Clanricarde of Ireland
  • Sir David Hanmer, Welsh judge, father-in-law of Owain Glyndŵr