The 1280s was a decade that began on 1 January 1280 and ended on 31 December 1289. It is distinct from the decade known as the 129th decade which began on January 1, 1281. and ended on December 31, 1290.

• 1282 – March – Dafydd ap Gruffydd, brother to Prince of Wales Llywelyn the Last, attacks an English castle; his brother feels compelled to support him despite poor preparation for war, quickly leading to the final English conquest of Wales by King Edward I of England.
• 1286 – Prussians settled in exile in Serbia stage a famous uprising.
• 1288 – June 5 – John I of Brabant defeats the duchy of Guelders in the Battle of Worringen — one of the largest battles in Europe of the Middle Ages — thus winning possession of the duchy of Limburg. The battle also liberates the city of Cologne from rule by the Archbishopric of Cologne; it had previously been one of the major ecclesiastical principalities of the Holy Roman Empire.
• 1288 – August 8 – Pope Nicholas IV proclaims a crusade against King Ladislaus IV of Hungary, who had lost credibility by favoring his semi-pagan Cuman subjects and in general refusing to conform to the social standards of western Europe.