The 1280s is the decade starting January 1, 1280 and ending December 31, 1289.
Europe in the 1280s was marked by naval warfare on the Mediterranean and consolidation of power by the major states. Ongoing struggles over the control of Sicily provoked lengthy naval warfare: after the Sicilian Vespers rebellion, the French Angevins struggled against Aragon for control of the island. King Rudolph I of Germany established the Habsburg dynasty in Austria when he invested his two sons with power there. In England, King Edward I of England completed the conquest of Wales and annexed the territory via the Statute of Rhuddlan; he also constructed a series of castles in Wales to suppress any future rebellions. Edward I also established several important legal traditions, including a court system to hear claims on the king's behalf and a codification of the separation of church and state legal powers. The death of King Alexander III of Scotland fomented political wrangling in Scotland which would soon lead to increased English influence over Scotland. In Sweden, King Magnus I of Sweden founded a Swedish nobility.
In Asia, the Mongols continued to expand their territories, although at a slower pace and with less success than in previous decades. Kublai Khan's Yuan Dynasty established control over the Khmer Empire in Cambodia, the Pagan Empire in Myanmar, and a kingdom of Laos, but failed a second attempted invasion of Japan and was twice defeated in attempted invasions of Vietnam. The Thai kingdoms of Lanna and Sukhothai also exercised power in the region, avoiding conflict with the Yuan Dynasty to the north. Across the continent in the Middle East, the Mamluk sultanate of Egypt continued to extinguish crusader states under the leadership of Qalawun, capturing Margat, Latakia, and the County of Tripoli. In Anatolia, Osman I became a local chief, or bey, planting the seed that would eventually grow into the Ottoman Empire.
The 1280s was also a busy decade in culture. In Thailand, King Ramkhamhaeng the Great invented the Thai alphabet. In the Netherlands, the St. Lucia's flood killed 50,000 while creating the Zuider Zee, thus giving Amsterdam the sea access it would later need to rise to prominence as an important port. In legal reforms, King Edward I of England started the use of drawing and quartering as punishment for traitors, King Philip IV of France created the gabelle, an onerous tax on salt, and the Scots Parliament passed laws allowing women to propose marriage to men, but only in leap years. The northern branch of the Grand Canal of China was constructed during the first half of the decade, the Uppsala Cathedral was begun, and a partial collapse set back construction of the Cathédrale Saint-Pierre de Beauvais in a blow to the aspirations of its Gothic architecture. Colleges at the Universities of Oxford and Cambridge were founded. The cities of Al Mansurah, Egypt and Guiyang, China were founded, while Hamburg, Germany burnt to the ground in a catastrophic fire. Jews continued to be persecuted across Europe, while Taoists suffered under Kublai Khan's Yuan Dynasty in China.