1271

1271 (MCCLXXI) was a common year starting on Thursday of the Julian calendar, the 1271st year of the Common Era (CE) and Anno Domini (AD) designations, the 271st year of the 2nd millennium, the 71st year of the 13th century, and the 2nd year of the 1270s decade. As of the start of 1271, the Gregorian calendar was 7 days ahead of the Julian calendar, which was the dominant calendar of the time.

• July 2 – Kings Otakar II of Bohemia and Stephen V of Hungary sign the first Peace of Pressburg, settling territorial claims following the failed invasion of Hungary by Otakar II.
• September 1 – Pope Gregory X succeeds Pope Clement IV as the 184th popeas the compromise candidate between French and Italian cardinals, ending a three-year conclave, the longest ever.
• The County of Toulouse is returned to the crown of France.
• Marco Polo departs from Venice with his father and uncle on his famous journey to Kublai Khan's China.
• The construction of Caerphilly Castle, the largest in Wales, is completed.
• Construction of the Belaya Vezha in Belarus is begun.

• April 8 – Mamluk sultan Baibars continues his territorial expansion, capturing the strategically important castle Krak des Chevaliers from the Knights Hospitaller in present-day Syria.
• Mamluk sultan Baibars conducts an unsuccessful siege of the city of Tripoli, and also fails in an attempted naval invasion of Cyprus.
• Edward I of England and Charles of Anjou arrive in Acre, starting the Ninth Crusade against Baibars; however, they are unable to capture any territory and a peace is quickly negotiated.

• September 12 – According to the followers of Nichiren Buddhism, the sect's founder, Nichiren, reaches a turning point known as hosshaku kempon as he discards his identity as a mortal priest and begins to reveal himself as a reincarnation of the Buddha.
• December 18 – Kublai Khan renames his empire "Yuan" (元 yuán), officially marking the start of the Yuan Dynasty of China.
• The Nakhi kingdom of the northern Himalayan foothills is annexed by the Yuan Dynasty.

• May 25 – Shah Jalal of Bengal (d. 1346)
• May – Joan of Acre, daughter of King Edward I of England (d. 1307)