1291 (MCCXCI) was a common year starting on Monday of the Julian calendar, the 1291st year of the Common Era (CE) and Anno Domini (AD) designations, the 291st year of the 2ndmillennium, the 91st year of the 13thcentury, and the 2nd year of the 1290s decade. As of the start of 1291, the Gregorian calendar was 7 days ahead of the Julian calendar, which was the dominant calendar of the time.

• The Crusades end.
• Switzerland was founded.

• February 8 – King Afonso IV of Portugal (d. 1357)
• October 31 – Philippe de Vitry, French composer (d. 1361)
• Pope Clement VI (d. 1352)
• Theodore I of Montferrat (d. 1338)
• Aimone of Savoy (d. 1343)

• March 10 – Arghun, Mongol ruler
• June 18 – King Alfonso III of Aragon (b. 1265)
• June 26 – Eleanor of Provence, queen of Henry III of England
• July 15 – Rudolph I of Germany, Holy Roman Emperor (b. 1218)
• Hong Dagu, Korean military leader (b. 1244)
• Talabuga, khan of the Blue Horde