The Battle of Montiel was a battle fought on 14 March 1369 between the Franco-Castilian forces supporting Henry of Trastámara and the Granadian-Castilian forces supporting the reigning Peter of Castile. The Franco-Castilians were victorious largely thanks to the enveloping tactics of du Guesclin.

After the battle, Peter fled to the castle of Montiel, where he became trapped. In an attempt to bribe Bertrand du Guesclin, Peter was lured into a trap outside his castle refuge. In the confrontation his half-brother Henry stabbed Peter multiple times. His death on 23 March 1369 marked the end of the Castilian Civil War. His victorious half-brother was crowned Henry II of Castille.

Henry made du Guesclin Duke of Molina and formed an alliance with the French King Charles V. Between 1370 and 1376, the Castilian fleet provided naval support to French campaigns against Aquitaine and the English coast while du Guesclin recaptured Poitou and Normandy from the English.